A Thermus thermophilus lytic phage was isolated from a Japanese hot spring by using a type IV pili-deficient strain as an indicator host, and designated as φMN1. Electron microscopic (EM) examination revealed that φMN1 had an icosahedral head and a contractile tail, suggesting that φMN1 belonged to Myoviridae. An EM analysis focused on φMN1 adsorption to the Thermus host cell showed that the receptor molecules for the phage were uniformly distributed on the outer surface of the cells. The circular double-stranded DNA of φMN1 was 76,659 base pairs in length, and the guanine and cytosine content was 61.8%. It was predicted to contain 99 open reading frames, and its putative distal tail fiber protein, which is essential for non-piliated host cell surface receptor recognition, was dissimilar in terms of sequence and length with its counterpart in the type IV pili-dependent φYS40. A phage proteomic tree revealed that φMN1 and φYS40 are in the same cluster, but many genes had low sequence similarities and some seemed to be derived from both mesophilic and thermophilic organisms. The gene organization suggested that φMN1 evolved from a non-Thermus phage through large-scale recombination events of the genes determining the host specificity, followed by gradual evolution by recombination of both the thermophilic and mesophilic DNAs assimilated by the host Thermus cells. This newly isolated phage will provide evolutionary insights into thermophilic phages.

In thermophilic microorganisms, c-type cytochrome (cyt) proteins mainly function in the respiratory chain as electron carriers. Genome analyses at the beginning of this century revealed a variety of genes harboring the heme c motif. Here, we describe the results of surveying genes with the heme c motif, CxxCH, in a genome database comprising four strains of Thermus thermophilus, including strain HB8, and the confirmation of 19 c-type cytochromes among 27 selected genes. We analyzed the 19 genes, including the expression of four, by a bioinformatics approach to elucidate their individual attributes. One of the approaches included an analysis based on the secondary structure alignment pattern between the heme c motif and the 6th ligand. The predicted structures revealed many cyt c domains with fewer β-strands, such as mitochondrial cyt c, in addition to the β-strand unique to Thermus inserted in cyt c domains, as in T. thermophilus cyt c552 and caa3 cyt c oxidase subunit IIc. The surveyed thermophiles harbor potential proteins with a variety of cyt c folds. The gene analyses led to the development of an index for the classification of cyt c domains. Based on these results, we propose names for T. thermophilus genes harboring the cyt c fold.

Thermus thermophilus has several minor lipid molecules with structures that have not been described yet. In this study, we identified a new lipid molecule in T. thermophilus HB8 with an amino group at the polar head, by detecting lipid spots with HPTLC and mass spectrometry. The structure of the lipid resembles an amino sugar phospholipid, except for the glucosamine that lacks an acetyl group. We named this amino phosphoglycolipid PGLN, and proposed its synthetic pathway from a precursor, phosphatidyl-glyceric alkylamine. The primary amine structure of PGLN may contribute to high temperature adaptation through electrostatic interactions between the head groups.

Abstract

Single-cell genomics is applied to environmental samples as a method to solve the problems of current metagenomics. However, in the fluorescence-activated cell sorting-based cell isolation and subsequent whole genome amplification, the sorting efficiency and the sequence quality are greatly affected by the type of target environment, limiting its adaptability. Here, we developed an improved single-cell genomics platform, named SAG-gel, which utilizes gel beads for single-cell isolation, lysis, and whole genome amplification. To validate the versatility of SAG-gel, single-cell genome sequencing was performed with model bacteria and microbial samples collected from eight environmental sites, including soil and seawater. Gel beads enabled multiple lysis treatments. The genome coverage with model bacteria was improved by 9.1–25%. A total of 734 single amplified genomes were collected from the diverse environmental samples, and almost full-length 16S rRNA genes were recovered from 57.8% of them. We also revealed two marine Rhodobacter strains harboring nearly identical 16S rRNA genes but having different genome contents. In addition, searching for viral sequences elucidated the virus-host linkage over the sampling sites, revealing the geographic distribution and diverse host range of viruses.

ABSTRACT

During the development of the mammalian brain, neocortical structures are formed by the sequential radial migration of newborn excitatory neurons. The early migrating neurons exhibit a multipolar shape, but they undergo a multipolar-to-bipolar transition at the subplate (SP) layer, where extracellular matrix (ECM) components are abundantly expressed. In this study, we revealed that the TGF-β signaling-related ECM proteins, such as latent TGF-β-binding protein 1 (LTBP1) and fibrillin 2, and TGF-β receptor II (TGF-βRII) and its downstream effector, p-smad2/3, are selectively expressed at the SP layer, suggesting that TGF-β is sequestered in a latent form by forming complexes with these ECM components and then its signaling is activated by ECM remodeling. We found that the migrating multipolar neurons transiently express a disintegrin and metalloproteinase with thrombospondin motif 2 (ADAMTS2), an ECM metalloproteinase, just below the SP layer. Knockdown and knockout of Adamts2 suppressed the multipolar-to-bipolar transition of migrating neurons, and therefore, disturbed radial migration. Similar phenotypes were observed by the perturbation of TGF-β signaling in the migrating neurons. Time-lapse luminescence imaging of TGF-β signaling indicated that ADAMTS2 activates this signaling pathway in the migrating neurons during the multipolar-to-bipolar transition at the SP layer. These results suggest that the ADAMTS2 secreted by the migrating multipolar neurons activates TGF-β signaling by ECM remodeling of the SP layer, leading to the multipolar-to-bipolar transition. We propose that the SP layer plays an essential role in the radial neuronal migration as a signaling center of the developing neocortex.

SIGNIFICANCE

The neocortex is formed by the sequential radial migration of newborn neurons, which undergo a multipolar-to-bipolar transition at the subplate (SP) layer. The extracellular matrix (ECM) is abundantly expressed in the SP layer. However, the roles of the ECM in the SP layer have been unclear. We found that migrating neurons transiently express a disintegrin and a metalloproteinase with thrombospondin motif 2 (ADAMTS2), an ECM metalloproteinase, just below the SP layer. We show that ADAMTS2 secreted by multipolar migrating neurons activates TGF-β signaling through remodeling of the ECM in the SP layer, leading to the multipolar-to-bipolar transition. Thus, the SP layer plays an essential role in radial migration as a signaling center of the developing neocortex

Abstract

Endozoicomonas bacteria symbiose with various marine organisms and are known to be beneficial for coral health. However, genome analysis of coral-associated Endozoicomonas has been limited owing to the difficulty in cultivation and metagenomic approach by contamination of host-derived sequences. In this study, we applied a novel single-cell genomics technique using droplet microfluidics to obtain single-cell amplified genome (SAGs) for coral-associated Endozoicomonas spp. genome. We obtained seven novel Endozoicomonas genomes from Acropora tenuis coral. These genomes revealed that Endozoicomonas bacteria played host-associated functions in host corals and had undergone independent host-adaptive evolution in different clades. These adaptive evolutions were mediated by host-derived eukaryotic-like genes, some of which were speculated to influence host immune mechanisms. These genes are speculated to enhance coral tolerance to environmental stresses. This study suggests the possibility of host adaptation of Endozoicomonas spp. in symbiosis with corals and their contribution to coral bleaching tolerance.

<jats:title>Abstract</jats:title><jats:sec>
<jats:title>Background</jats:title>
<jats:p>Canalization, or buffering, is defined as developmental stability in the face of genetic and/or environmental perturbations. Understanding how canalization works is important in predicting how species survive environmental change, as well as deciphering how development can be altered in the evolutionary process. However, how developmental gene expression is linked to buffering remains unclear. We addressed this by co-expression network analysis, comparing gene expression changes caused by heat stress during development at a whole-embryonic scale in reciprocal hybrid crosses of sibling species of the ascidian <jats:italic>Ciona</jats:italic> that are adapted to different thermal environments.</jats:p>
</jats:sec><jats:sec>
<jats:title>Results</jats:title>
<jats:p>Since our previous work showed that developmental buffering in this group is maternally inherited, we first identified maternal developmental buffering genes (MDBGs) in which the expression level in embryos is both correlated to the level of environmental canalization and also differentially expressed depending on the species’ gender roles in hybrid crosses. We found only 15 MDBGs, all of which showed high correlation coefficient values for expression with a large number of other genes, and 14 of these belonged to a single co-expression module. We then calculated correlation coefficients of expression between MDBGs and transcription factors in the central nervous system (CNS) developmental gene network that had previously been identified experimentally. We found that, compared to the correlation coefficients between MDBGs, which had an average of 0.96, the MDBGs are loosely linked to the CNS developmental genes (average correlation coefficient 0.45). Further, we investigated the correlation of each developmental to MDBGs, showing that only four out of 62 CNS developmental genes showed correlation coefficient &gt; 0.9, comparable to the values between MDBGs, and three of these four genes were signaling molecules: BMP2/4, Wnt7, and Delta-like.</jats:p>
</jats:sec><jats:sec>
<jats:title>Conclusions</jats:title>
<jats:p>We show that the developmental pathway is not centrally located within the buffering network. We found that out of 62 genes in the developmental gene network, only four genes showed correlation coefficients as high as between MDBGs. We propose that loose links to MDBGs stabilize spatiotemporally dynamic development.</jats:p>
</jats:sec>

Abstract

The production of bioactive metabolites is increasingly recognized as an important function of host-associated bacteria. An example is defensive symbiosis that might account for much of the chemical richness of marine invertebrates including sponges (Porifera), 1 of the oldest metazoans. However, most bacterial members of sponge microbiomes have not been cultivated or sequenced, and therefore, remain unrecognized. Unequivocally linking metabolic functions to a cellular source in sponge microbiomes is, therefore, a challenge. Here, we report an analysis pipeline of microfluidic encapsulation, Raman microscopy, and integrated digital genomics (MERMAID) for an efficient identification of uncultivated producers. We applied this method to the chemically rich bacteriosponge (sponge that hosts a rich bacterial community) Theonella swinhoei, previously shown to contain ‘Entotheonella’ symbionts that produce most of the bioactive substances isolated from the sponge. As an exception, the antifungal aurantosides had remained unassigned to a source. Raman-guided single-bacterial analysis and sequencing revealed a cryptic, distinct multiproducer, ‘Candidatus Poriflexus aureus’ from a new Chloroflexi lineage as the aurantoside producer. Its exceptionally large genome contains numerous biosynthetic loci and suggested an even higher chemical richness of this sponge than previously appreciated. This study highlights the importance of complementary technologies to uncover microbiome functions, reveals remarkable parallels between distantly related symbionts of the same host, and adds functional support for diverse chemically prolific lineages being present in microbial dark matter.

<jats:p> Ovarian clear cell carcinoma (OCCC), one of the histopathological types of ovarian cancer, has a poor prognosis when it recurs; however, it is difficult to precisely predict the risk of recurrence. Here, we analyzed pathological images of OCCC to elucidate the relationship between pathological findings and recurrence, and using machine learning, we established a classifier to predict the recurrence and several other prognosis indicators of this disease. In total, 110 patients with OCCC treated with primary surgery at a single institution were enrolled in this study. We used the deep-learning neural networks to process the whole slide images of OCCC obtained by digitally scanning the original hematoxylin and eosin-stained glass slides. The images were preprocessed and used as input to the machine learning pipeline. We fine-tuned its parameters to predict the recurrence, progression-free survival, and the overall survival days of all patients. We predicted the recurrence of OCCC with an overall accuracy of 93%, area under the receiver operating characteristic curve of 0.98, and sensitivity/specificity above 0.92 using Resnet 34. Furthermore, we predicted progression-free survival/overall survival of the patients with ~90% accuracy. In conclusion, our study demonstrates the feasibility of using a machine learning system to predict different features of OCCC samples using histopathological images as input. This novel application provides accurate prognosis information and aids in the development of personalized treatment strategies. </jats:p>

Abstract

Cleavage and polyadenylation at the 3ʹ end of the pre-mRNA is essential for mRNA function, by regulating its translatability, stability and translocation to the cytoplasm. Cleavage factor I (CFI) is a multi-subunit component of the pre-mRNA 3ʹ end processing machinery in eukaryotes. Here, we report that plant CFI 25 subunit of CFI plays an important role in maintaining the diversity of the 3ʹ ends of mRNA. The genome of Arabidopsis thaliana (L.) Heynh. contained four genes encoding three putative CFI subunits (AtCFI 25, AtCFI 59 and AtCFI 68), orthologous to the mammalian CFI subunits. There were two CFI 25 paralogs (AtCFI 25a and AtCFI 25b) that shared homology with human CFI 25. Two null alleles of AtCFI 25a displayed smaller rosette leaves, longer stigmatic papilla, smaller anther, earlier flowering and lower fertility compared to wild-type plants. Null alleles of AtCFI 25b, as well as, plants ectopically expressing full-length cDNA of AtCFI 25a, displayed no obvious morphological defects. AtCFI 25a was shown to interact with AtCFI 25b, AtCFI 68 and itself, suggesting various forms of CFI in plants. Furthermore, we show that AtCFI 25a function was essential for maintaining proper diversity of the 3ʹ end lengths of transcripts coding for CFI subunits, suggesting a self-regulation of the CFI machinery in plants. AtCFI 25a was also important to maintain 3ʹ ends for other genes to different extent. Collectively, AtCFI 25a, but not AtCFI 25b, seemed to play important roles during Arabidopsis development by maintaining proper diversity of the 3ʹ UTR lengths.

BACKGROUND: Many drugs have the potential to induce the expression of drug-metabolizing enzymes, particularly cytochrome P450 3A4 (CYP3A4), in hepatocytes. Hepatocytes can be accurately evaluated for drug-mediated CYP3A4 induction; this is the gold standard for in vitro hepatic toxicology testing. However, the variation from lot to lot is an issue that needs to be addressed. Only a limited number of immortalized hepatocyte cell lines have been reported. In this study, immortalized cells expressing CYP3A4 were generated from a patient with drug-induced liver injury (DILI). METHODS: To generate DILI-derived cells with high expression of CYP3A4, a three-step approach was employed: (1) Differentiation of DILI-induced pluripotent stem cells (DILI-iPSCs); (2) Immortalization of the differentiated cells; (3) Selection of the cells by puromycin. It was hypothesized that cells with high cytochrome P450 gene expression would be able to survive exposure to cytotoxic antibiotics because of their increased drug-metabolizing activity. Puromycin, a cytotoxic antibiotic, was used in this study because of its rapid cytocidal effect at low concentrations. RESULTS: The hepatocyte-like cells differentiated from DILI-iPSCs were purified by exposure to puromycin. The puromycin-selected cells (HepaSM or SI cells) constitutively expressed the CYP3A4 gene at extremely high levels and exhibited hepatocytic features over time. However, unlike primary hepatocytes, the established cells did not produce bile or accumulate glycogen. CONCLUSIONS: iPSC-derived hepatocyte-like cells with intrinsic drug-metabolizing enzymes can be purified from non-hepatocytes and undifferentiated iPSCs using the cytocidal antibiotic puromycin. The puromycin-selected hepatocyte-like cells exhibited characteristics of hepatocytes after immortalization and may serve as another useful source for in vitro hepatotoxicity testing of low molecular weight drugs.

Protein Data Bank Japan (PDBj), a founding member of the worldwide Protein Data Bank (wwPDB) has accepted, processed and distributed experimentally determined biological macromolecular structures for 20 years. During that time, we have continuously made major improvements to our query search interface of PDBj Mine 2, the BMRBj web interface, and EM Navigator for PDB/BMRB/EMDB entries. PDBj also serves PDB-related secondary database data, original web-based modeling services such as Homology modeling of complex structure (HOMCOS), visualization services and utility tools, which we have continuously enhanced and expanded throughout the years. In addition, we have recently developed several unique archives, BSM-Arc for computational structure models, and XRDa for raw X-ray diffraction images, both of which promote open science in the structural biology community. During the COVID-19 pandemic, PDBj has also started to provide feature pages for COVID-19 related entries across all available archives at PDBj from raw experimental data and PDB structural data to computationally predicted models, while also providing COVID-19 outreach content for high school students and teachers.

Abstract

Corals create an ecosystem, called a holobiont, with intracellular algae (zooxanthellae) and resident bacteria. Zooxanthellae and some bacteria play major roles in the physiological properties of the coral host. However, because of the difficulties in experimental verification of cross-organism interactions, the mechanisms underpinning these interactions are largely unknown. To address this, we here generated and then analyzed multi-omics datasets for corals, zooxanthellae, and bacteria collected at Okinawa, Japan, from November 2014 to September 2016. Using cross-organism co-expression analysis, we successfully characterized the host–alga relationship in the coral holobiont. Specifically, we observed that the coral host dominates the zooxanthellae. The multi-omics analysis also suggested that infection with coral-associated bacteria Endozoicomonas likely involves coral-like ephrin ligands, triggering an immune response of the coral host. This study highlights the potential of the multi-omics approach to elucidate coral–microbe interactions.

Species of infraorder Gryllidea, or crickets, are useful invertebrate models for studying developmental biology and neuroscience. They have also attracted attention as alternative protein sources for human food and animal feed. Mitochondrial genomic information on related invertebrates, such as katydids, and locusts, has recently become available in attempt to clarify the controversial classification schemes, although robust phylogenetic relationships with emphasis on crickets remain elusive. Here, we report newly sequenced complete mitochondrial genomes of crickets to study their phylogeny, genomic rearrangements, and adaptive evolution. First, we conducted de novo assembly of mitochondrial genomes from eight cricket species and annotated protein-coding genes (PCGs) and transfer and ribosomal RNAs using automatic annotations and manual curation. Next, by combining newly described PCGs with public data of the complete Gryllidea genomes and gene annotations, we performed phylogenetic analysis and found gene order rearrangements in several branches. We further analyzed genetic signatures of selection in ant-loving crickets (Myrmecophilidae), which are small wingless crickets that inhabit ant nests. Three distinct approaches revealed two positively selected sites in the cox1 gene in these crickets. Protein 3D structural analyses suggested that these selected sites could influence the interaction of respiratory complex proteins, conferring benefits to ant-loving crickets with a unique ecological niche and morphology. These findings enhance our understanding of the genetic basis of cricket evolution without relying on estimates based on a limited number of molecular markers.

Streptomyces incarnatus NRRL8089 produces the antiviral, antifungal, antiprotozoal nucleoside antibiotic sinefungin. To enhance sinefungin production, multiple mutations were introduced to the rpoB gene encoding RNA polymerase (RNAP) β-subunit at the target residues, D447, S453, H457, and R460. Sparse regression analysis using elastic-net lasso-ridge penalties on previously reported H457X mutations identified a numeric parameter set, which suggested that H457R/Y/F may cause production enhancement. H457R/R460C mutation successfully enhanced the sinefungin production by 3-fold, while other groups of mutations, such as D447G/R460C or D447G/H457Y, made moderate or even negative effects. To identify why the rif cluster residues have diverse effects on sinefungin production, an RNAP/DNA/mRNA complex model was constructed by homology modeling and molecular dynamics simulation. The 4 residues were located near the mRNA strand. Density functional theory-based calculation suggested that D447, H457, and R460 are in direct contact with ribonucleotide, and partially positive charges are induced by negatively charged chain of mRNA.

COP9 signalosome (CSN) is a nuclear complex composed of eight distinct subunits that governs vast developmental processes in Arabidopsis thaliana (L.) Heynh. The null alleles of csn mutants display pleiotropic phenotypes that result in seedling lethality. To date, several partially complemented transgenic plants, expressing the particular CSN subunit in its corresponding null mutant allele, were utilized to bypass seedling lethality and investigate CSN regulation at later stages of development. One such transgenic plant corresponding to CSN1 subunit, fus6/CSN1-3-4, accumulates wild-type level of CSN1 and displays normal plant architecture at vegetative stage. Here we show through histological analyses that fus6/CSN1-3-4 plants display impairment of pollen development at the bicellular stage. This defect is identical to that observed in RNAi plants of SAP130, encoding a subunit of the multiprotein splicing factor SF3b. We further dissected the previously reported interaction between CSN1 and SAP130, to reveal that approximately 100 amino-acid residues located at the N-terminal end of CSN1 (CSN1NN) were essential for this interaction. In silico structure modeling demonstrated that CSN1NN could swing out towards SAP130 to dock onto its Helical Insertion protruding from the structure. These results support our model that CSN1 embeds itself within CSN protein complex through its C-terminal half and reaches out to targets through its N-terminal portion of the protein. Taken together, this is the first report to document the identical loss-of-function phenotypes of CSN1 and SAP130 during male gametogenesis. Thus, we propose that SAP130 and CSN1 coordinately regulate development of male reproductive organs.

In this study, we present an analysis of metagenome sequences obtained from a filtrate of a siphon tissue homogenate of otter clams (Lutraria rhynchaena) with swollen-siphon disease. The viral signal was mined from the metagenomic data, and a novel circular ssDNA virus was identified. Genomic features and phylogenetic analysis showed that the virus belongs to the phylum Cressdnaviricota, which consists of viruses with circular, single-stranded DNA (ssDNA) genomes. Members of this phylum have been identified in various species and in environmental samples. The newly found virus is distantly related to the currently known members of the phylum Cressdnaviricota.

<jats:title>Abstract</jats:title><jats:p><jats:italic>Watasenia scintillans</jats:italic>, a sparkling enope squid, has bioluminescence organs to illuminate its body with its own luciferase activity. To clarify the molecular mechanism underlying its scintillation, we analysed high-throughput sequencing data acquired previously and obtained draft genome sequences accomplished with comparative genomic data among the cephalopods. The genome mapped by transcriptome data showed that (1) RNA editing contributed to transcriptome variation of lineage specific genes, such as <jats:italic>W. scintillans</jats:italic> luciferase, and (2) two types of luciferase enzymes were characterized with reasonable 3D models docked to a luciferin molecule. We report two different types of luciferase in one organism and possibly related to variety of colour types in the <jats:italic>W. scintillans</jats:italic> fluorescent organs.</jats:p>

BRCA1/2 genetic testing to use PARP inhibitor for breast cancer has a possibility of the "secondary finding" among the younger nonaffected family members of the patient, which turns them into at-risk for hereditary breast cancer. Proper understanding of the background of the hereditary cancer is now required for appropriate acceptance of the risk. Therefore, we investigated the level of knowledge and attitudes of younger women on hereditary breast cancer in Japan. Study subject was Japanese university women between 20 and 30 years of age, without medical history of breast cancer. We conducted the anonymous self-answering questionnaire to them. We received responses from 353 women. The levels of knowledge, awareness, and interest were relatively high. Women with a family history of breast cancer were less likely to undergo testing than women without (92.8% vs. 74.5%, p < 0.001). The rates of positive response toward risk-reducing mastectomy (RRM) and risk-reducing salpingo-oophorectomy (RRSO) was significantly high for medical majors compared with that for other majors (RRM: medical 71.6% vs. science 54.5% vs. humanities 53.8%, p = 0.008, RRSO: 35.4% vs. 36.3% vs. 48.4%, p = 0.027). Approximately half of respondents answered that they would hesitate to get married (45.3%) or to have children (55.4%), if they were a BRCA1/2 mutation carrier. The results may help to establish the methods for supporting the decision-making for reproduction of younger women who are unexpectedly labeled as being at-risk for HBOC.

Biophysics in Waseda University was started in 1965 as one of the three key research areas that constitute the Physics Department. In the biophysics group, one theoretical lab and two experimental labs are now working on the cutting-edge themes on biophysics, disseminating the ideas and knowledge of biophysics to undergraduate and graduate students from the viewpoint of physics.

Biophysics in Waseda University was started in 1965 as one of the three key research areas that constitute the Physics Department. In the biophysics group, one theoretical lab and two experimental labs are now working on the cutting-edge themes on biophysics, disseminating the ideas and knowledge of biophysics to undergraduate and graduate students from the viewpoint of physics.

© 2020 Kagaya et al. Otter clam farming in Vietnam has recently encountered difficulties due to swollen-siphon disease. Here, we report the metagenome sequences of microorganisms extracted from the siphon tissue of infected otter clams. The data comprised bacterial and viral sequences which likely include those derived from the disease-causing agent.

<title>Abstract</title>Potential inhibitors of a target biomolecule, NAD-dependent deacetylase Sirtuin 1, were identified by a contest-based approach, in which participants were asked to propose a prioritized list of 400 compounds from a designated compound library containing 2.5 million compounds using <italic>in silico</italic> methods and scoring. Our aim was to identify target enzyme inhibitors and to benchmark computer-aided drug discovery methods under the same experimental conditions. Collecting compound lists derived from various methods is advantageous for aggregating compounds with structurally diversified properties compared with the use of a single method. The inhibitory action on Sirtuin 1 of approximately half of the proposed compounds was experimentally accessed. Ultimately, seven structurally diverse compounds were identified.

Caspase-3-related DEVDase activity is initiated upon apoptosis in unfertilized starfish eggs. In this study, we cloned a starfish procaspase-3 corresponding to mammalian effector caspase containing a CARD that is similar to the amino terminal CARD of mammalian capsase-9, and we named it procaspase-3/9. Recombinant procaspase-3/9 expressed at 15 °C was cleaved to form active caspase-3/9 which has DEVDase activity. Microinjection of the active caspase-3/9 into starfish oocytes/eggs induced apoptosis. An antibody against the recombinant protein recognized endogenous procaspase-3/9 in starfish oocytes, which was cleaved upon apoptosis in aged unfertilized eggs. These results indicate that caspase-3/9 is an effector caspase in starfish. To verify the mechanism of caspase-3/9 activation, we cloned starfish Apaf-1 containing a CARD, a NOD, and 11 WD40 repeat regions, and we named it sfApaf-1. Recombinant sfApaf-1 CARD interacts with recombinant caspase-3/9 CARD and with endogenous procaspase-3/9 in cell-free preparations made from starfish oocytes, causing the formation of active caspase-3/9. When the cell-free preparation without mitochondria was incubated with inactive recombinant procaspase-3/9 expressed at 37 °C, DEVDase activity increased and apoptosome-like complexes were formed in the high molecular weight fractions containing both sfApaf-1 and cleaved caspase-3/9. These results suggest that sfApaf-1 activation is not dependent on cytochrome c.

The neocortex exhibits a six-layered structure that is formed by radial migration of excitatory neurons, for which the multipolar-to-bipolar transition of immature migrating multipolar neurons is required. Here, we report that subplate neurons, one of the first neuron types born in the neocortex, manage the multipolar-to-bipolar transition of migrating neurons. By histochemical, imaging, and microarray analyses on the mouse embryonic cortex, we found that subplate neurons extend neurites toward the ventricular side of the subplate and form transient glutamatergic synapses on the multipolar neurons just below the subplate. NMDAR (N-methyl-D-aspartate receptor)-mediated synaptic transmission from subplate neurons to multipolar neurons induces themultipolar-to-bipolar transition, leading to a change inmigration mode from slow multipolar migration to faster radial glial-guided locomotion. Our data suggested that transient synapses formed on early immature neurons regulate radialmigration.

Background: More than 7000 papers related to "protein refolding" have been published to date, with approximately 300 reports each year during the last decade. Whilst some of these papers provide experimental protocols for protein refolding, a survey in the structural life science communities showed a necessity for a comprehensive database for refolding techniques. We therefore have developed a new resource "REFOLDdb" that collects refolding techniques into a single, searchable repository to help researchers develop refolding protocols for proteins of interest.
Results: We based our resource on the existing REFOLD database, which has not been updated since 2009. We redesigned the data format to be more concise, allowing consistent representations among data entries compared with the original REFOLD database. The remodeled data architecture enhances the search efficiency and improves the sustainability of the database. After an exhaustive literature search we added experimental refolding protocols from reports published 2009 to early 2017. In addition to this new data, we fully converted and integrated existing REFOLD data into our new resource. REFOLDdb contains 1877 entries as of March 17th, 2017, and is freely available at http://p4d-info.nig.ac.jp/refolddb/.
Conclusion: REFOLDdb is a unique database for the life sciences research community, providing annotated information for designing new refolding protocols and customizing existing methodologies. We envisage that this resource will find wide utility across broad disciplines that rely on the production of pure, active, recombinant proteins. Furthermore, the database also provides a useful overview of the recent trends and statistics in refolding technology development.

Protein is the major component of the organism. A concave (pocket) on a protein surface is known to be thebest target for a drug to react. We previously presented astudy on distance analysis between pockets and amino acidresidue. We firstly identified pockets on the protein surfaceand then calculated distances between atoms of an amino acidresidue and the deepest points or the outer loops of the pockets. We extracted proteins which at least one of the pockets areclose to arbitrary pairs of amino acid residues, calculated theratios of druggable proteins, and visualized the distributionof the ratios as a colored matrix. We suggested from thevisualization results that particular pairs of amino acid residuesmay affect the druggability of the proteins in our previousstudy. This paper presents an extension of our study to explorethe relevance between druggability of proteins and distancesbetween a set of amino acid residues and protein surfacepockets. Our technique treats the pockets as 20-dimensionalvectors consisting of distances to each of amino acid residues, and applies GeodesicSOM with the set of the vectors. Sphericalmaps generated by GeodesicSOM are used to visualizationof distribution of the pockets in the 20-dimensional vectorspace, and estimation of druggability of proteins with the 20-dimensional vectors of the pockets.

The sparkling enope squid, Watasenia scintillans, is a deep-sea mollusk inhabiting the western part of the Pacific Ocean. It has the peculiar ability to illuminate its body without the involvement of other organisms. In this study, we extracted the brain DNA from a single squid female caught in the Japan Sea and determined the complete genome sequence of its mitochondrial DNA using the Illumina sequencing platform. The circular sequence is 20,089 bp in length. Using the next-generation sequencing data, we also estimated the mean copy number of mitochondria per cell in the brain to be 108 by comparig the depths of the read data in the nuclear and mitochondrial genomes. The haploid genome size was calculated to be 4.78 Gb. Six heteroplasmy sites were also identified, together with their allele frequencies, in this individual. Our methodology is shown to be useful in mitochondrion-related studies.

<p>We investigated the effect of ATP binding to GroEL and elucidated a role of ATP in the conformational change of GroEL. GroEL is a tetradecamer chaperonin that helps protein folding by undergoing a conformational change from a closed state to an open state. This conformational change requires ATP, but does not require the hydrolysis of the ATP. The following three types of conformations are crystalized and the atomic coordinates are available; closed state without ATP, closed state with ATP and open state with ADP. We conducted simulations of the conformational change using Elastic Network Model from the closed state without ATP targeting at the open state, and from the closed state with ATP targeting at the open state. The simulations emphasizing the lowest normal mode showed that the one started with the closed state with ATP, rather than the one without ATP, reached a conformation closer to the open state. This difference was mainly caused by the changes in the positions of residues in the initial structure rather than the changes in "connectivity" of residues within the subunit. Our results suggest that ATP should behave as an insulator to induce conformation population shift in the closed state to the conformation that has a pathway leading to the open state.</p>

Life science research now heavily relies on all sorts of databases for genome sequences, transcription, protein three-dimensional (3D) structures, protein–protein interactions, phenotypes and so forth. The knowledge accumulated by all the omics research is so vast that a computer-aided search of data is now a prerequisite for starting a new study. In addition, a combinatory search throughout these databases has a chance to extract new ideas and new hypotheses that can be examined by wet-lab experiments. By virtually integrating the related databases on the Internet, we have built a new web application that facilitates life science researchers for retrieving experts’ knowledge stored in the databases and for building a new hypothesis of the research target. This web application, named VaProS, puts stress on the interconnection between the functional information of genome sequences and protein 3D structures, such as structural effect of the gene mutation. In this manuscript, we present the notion of VaProS, the databases and tools that can be accessed without any knowledge of database locations and data formats, and the power of search exemplified in quest of the molecular mechanisms of lysosomal storage disease. VaProS can be freely accessed at http://p4d-info.nig.ac.jp/vapros/.

Lampreys are eel-like jawless fishes evolutionarily positioned between invertebrates and vertebrates, and have been used as model organisms to explore vertebrate evolution. In this study we determined the complete genome sequence of the mitochondrial DNA of the Japanese river lamprey, Lethenteron japonicum, using next-generation sequencers. The sequence was 16,272 bp in length. The gene content and order were identical to those of the sea lamprey, Petromyzon marinus, which has been the reference among lamprey species. However, the sequence similarity was less than 90%, suggesting the need for the whole-genome sequencing of L. japonicum.

Eye-field transcription factors (EFTFs) are a set of genes that compose a regulatory network for eye development in animals, which are highly conserved among various animal phyla. To investigate the processes of conservation and diversification of the transcription factors for eye development, we examined the structural changes in the EFTF proteins by estimating the ancestral sequences with the available genome information. Among the different types of EFTFs, we selected otx2, tbx3, rx1, pax6, six3/6, Ihx2 and nr2e1 because they are highly conserved in bilaterian animals. We searched the genome sequences of representative animal phyla for EFTF protein sequences. With deduced ancestral sequences and three-dimensional structures of EFTFs, we traced the evolutionary changes in amino add residues and found that the DNA-binding domains were always more conserved than other regions, and that the other regions showed distinct evolutionary rates. The EFTF rx1, which resides at the pivotal part of the EFTF network, had a faster evolutionary rate than the others. These results indicated that the evolutionary rates of each protein in the EFTF network, which were expected to be consistent with each other to maintain the interactions in the network, were not constant among or within the factors, but rather, varied to a significant extent. (C) 2014 Published by Elsevier B.V.

Steroid hormone is extensively used for transmitting variety of biological signals in organisms. Natural steroid hormone is synthesized from cholesterol in adrenal cortex and in sexual gland in vertebrates. Appropriately dosed synthetic steroid hormones can be used for medication. Despite their positive effects as medicine, they sometimes cause significant side effects due to their wide range of actions, and the studies for discovering the mechanisms of side effects were carried out aiming to reduce the side effects. The fundamental cause of the side effects seems to be interactions between the steroid and a non-target protein. To understand the possible range of interaction of steroid molecule, we gathered all the three-dimensional structures of protein-steroid complex determined by X-ray crystallography, compared the atomic environments of the steroid-binding sites in proteins and classified the pattern of steroid binding. Protein Data Bank contained 871 structures of steroid-protein complexes in 382 entries. For this study, we selected 832 steroid binding proteins. Using a newly developed method to describe the atomic environments of these steroid molecules and their function, we were able to separate the environments into six patterns. This classification had a potential to predict the function of function-unknown proteins with a co-crystallized steroid molecule. We speculated that the proteins grouped into the same pattern of nuclear receptors were the candidates of non-targeted proteins causing a side effect by a therapeutic prescription of steroid hormone. (C) 2015 Elsevier Inc. All rights reserved.

Tafazzin is a mitochondrial phospholipid transacylase, and its mutations cause Barth syndrome (BTHS). Human tafazzin gene produces four distinct alternatively spliced transcripts. To understand the molecular mechanisms of tafazzin deficiency, we performed an atomic resolution analysis of the influence of the BTHS mutations and of alternative splicing on the structure and function of tafazzin. From the three-dimensional (3D) homology modeling of tafazzin, we identified candidate amino acid residues that contribute to cardiolipin binding and to mitochondrial membrane associations that facilitate acyl-transfer reactions. Primate specific exon 5, which is alternatively spliced, is predicted to correspond to an intrinsically unstructured region in the protein. We proposed that this region should change the substrate-binding affinity and/or contribute to primate-specific molecular interactions. Exon 7, another alternatively spliced exon, encodes a region forming a part of the putative substrate-binding cleft, suggesting that the gene products lacking exon 7 will lose their substrate-binding ability. We demonstrate a clear localization of the BTHS mutations at residues responsible for membrane association, substrate binding, and the conformational stability of tafazzin. These findings provide new insights into the function of defective tafazzin and the pathogenesis of BTHS at the level of protein 3D structure and the evolution of alternatively spliced exons in primates.

The biochemical analysis of Phytolacca americana DOPA dioxygenases (PaDOD1 and PaDOD2) was carried out. The recombinant protein of PaDOD1 catalyzed the conversion of DOPA to betalamic acid, whereas DOD activity was not detected in PaDOD2 in vitro. While the reported motif conserved in DODs from betalain-producing plants was found in PaDOD1, a single amino acid residue alteration was detected in PaDOD2. A mutated PaDOD1 protein with a change of 177 Asn to Gly showed reduced specific activity compared with PaDOD1, while DOPA dioxygenase activity was not observed for a mutated PaDOD2 protein which had its conserved motif replaced with that of PaDOD1. A three-dimensional (3D) structural model of PaDOD1 and PaDOD2 showed that the conserved motif in DODs was located in the N-terminal side of a loop, which was found close to the putative active site. The difference in stability of the loop may affect the enzymatic activity of PaDOD2.

The androgen receptor (AR) plays important roles in multiple physiological functions, including differentiation, growth, and maintenance of male reproductive organs, and also has effects on hair and skin. In this paper, we report the synthesis of nonsteroidal AR antagonists having a 4-benzyl-1-(2H)-phthalazinone skeleton. Among the synthesized compounds, 11c with two ortho-substituents on the phenyl group potently inhibited SC-3 cell proliferation (IC50: 0.18 mu M) and showed high wt AR-binding affinity (IC50: 10.9 mu M), comparable to that of hydroxyflutamide (3). Compound 11c also inhibited proliferation of LNCaP cells containing T877A-mutated AR. Docking study of 11c with the AR ligand-binding domain indicated that the benzyl group is important for the antagonism. These phthalazinone derivatives may be useful for investigating potential clinical applications of AR antagonists. (C) 2015 Elsevier Masson SAS. All rights reserved.

Flagellar dyneins are essential microtubule motors in eukaryotes, as they drive the beating motions of cilia and flagella. Unlike myosin and kinesin motors, the track binding mechanism of dyneins and the regulation between the strong and weak binding states remain obscure. Here we report the solution structure of the microtubule-binding domain of flagellar dynein-c/DHC9 (dynein-c MTBD). The structure reveals a similar overall helix-rich fold to that of the MTBD of cytoplasmic dynein (cytoplasmic MTBD), but dynein-c MTBD has an additional flap, consisting of an antiparallel b sheet. The flap is positively charged and highly flexible. Despite the structural similarity to cytoplasmic MTBD, dynein-c MTBD shows only a small change in the microtubule- binding affinity depending on the registry change of coiled coil-sliding, whereby lacks the apparent strong binding state. The surface charge distribution of dynein-c MTBD also differs from that of cytoplasmic MTBD, which suggests a difference in the microtubule-binding mechanism.

Protein is the major component of the organism. It has a unique three-dimensional structure determined by its amino acid sequence. A concave (pocket) on the surface of a protein is known to be the best target for a drug to react. We started analyzing how' drug ability' of proteins related to the location of amino acids in a pocket. For as tarter of the study, this paper presents a visualization tool for distance analysis between pockets and the amino acid residue. Provided that a protein surface is described by a triangular mesh, this tool first identifies pockets on the protein surface, specifies the deepest point and outer loops of the pocket, and calculates distances between atoms of an amino acid residue and the deepest point or the outer loops of the pocket. The tool then visualizes the statistics of the distance calculation results by poly line charts and the distribution by scatter plots. This paper proposes a biological interpretation of the visualization results.

Previous studies have reported that the developmental processes of vertebrate eyes are controlled by four Pax-6 splicing variants, each modulating different downstream genes, whereas those of insect eyes are controlled by duplicated Pax-6 genes. Cephalopods belong to the Protostomes but possess a camera-type eye similar to those in vertebrates. We examined Pax-6 variations in the squid and found five types of Pax-6 splicing variants but no duplication of the Pax-6 gene. In the five splicing variants, the splicing patterns were produced by the combination of two additional exons to the ortholog and one jettisoned exon containing most of the Homeobox domain (HD). These five variants show spatio-temporal patterns of gene expression during development in the squid. Our study suggests that cephalopods acquired Pax-6 splicing variants independent of those in vertebrates and that these variants were similarly utilized in the development of the squid eye.

Metabolic enzymes utilize the cofactor flavin adenine dinucleotide (FAD) to catalyze essential biochemical reactions. Because these enzymes have been implicated in disease pathways, it will be necessary to target them via FAD-based structural analogues that can either activate/inhibit the enzymatic activity. To achieve this, it is important to explore the conformational space of FAD in the enzyme-bound and free states. Herein, we analyze X-ray crystallographic data of the enzyme-bound FAD conformations and sample conformations of the molecule in explicit water by molecular dynamics (MD) simulations. Enzyme-bound FAD conformations segregate into five distinct groups based on dihedral angle principal component analysis (PCA). A notable feature in the bound FADs is that the adenine base and isoalloxazine ring are oppositely oriented relative to the pyrophosphate axis characterized by near trans hypothetical dihedral angle ?V values. Not surprisingly, MD simulations in water show final compact but not perfectly stacked ring structures in FAD. Simulation data did not reveal noticeable changes in overall conformational dynamics of the dinucleotide in reduced and oxidized forms and in the presence and/or absence of ions. During unfoldingfolding dynamics, the riboflavin moiety is more flexible than the adenosine monophosphate group in the molecule. Conversely, the isoalloxazine ring is more stable than the variable adenine base. The pyrophosphate group depicts an unusually highly organized fluctuation illustrated by its dihedral angle distribution. Conformations sampled from enzymes and MD are quantified. The extent to which the protein shifts the distribution from the unbound state is discussed in terms of prevalent FAD shapes and dihedral angle population.

Flagellar dyneins are essential microtubule motors in eukaryotes, as they drive the beating motions of cilia and flagella. Unlike myosin and kinesin motors, the track binding mechanism of dyneins and the regulation between the strong and weak binding states remain obscure. Here we report the solution structure of the microtubule-binding domain of flagellar dynein-c/DHC9 (dynein-c MTBD). The structure reveals a similar overall helix-rich fold to that of the MTBD of cytoplasmic dynein (cytoplasmic MTBD), but dynein-c MTBD has an additional flap, consisting of an antiparallel beta sheet. The flap is positively charged and highly flexible. Despite the structural similarity to cytoplasmic MTBD, dynein-c MTBD shows only a small change in the microtubule-binding affinity depending on the registry change of coiled coil-sliding, whereby lacks the apparent strong binding state. The surface charge distribution of dynein-c MTBD also differs from that of cytoplasmic MTBD, which suggests a difference in the microtubule-binding mechanism.

Adenosine triphosphate (ATP) is a versatile molecule used mainly for energy and a phosphate source. The hydrolysis of γ phosphate initiates the reactions and these reactions almost always start when ATP binds to protein. Therefore, there should be a mechanism to prevent spontaneous hydrolysis reaction and a mechanism to lead ATP to a pure energy source or to a phosphate source. To address these questions, we extensively analyzed the effect of protein to ATP conformation based on the sampling of the ATP solution conformations obtained from molecular dynamics simulation and the sampling of ATP structures bound to protein found in a protein structure database. The comparison revealed mainly the following three points
1) The ribose ring in ATP molecule, which puckers in many ways in solution, tends to assume either C2′ exo or C2′ endo when it binds to protein. 2) The adenine ring in ATP molecule, which takes open-book motion with the two ring structures, has two distinct structures when ATP binds to protein. 3) The glycosyl-bond and the bond between phosphate and the ribose have unique torsion angles, when ATP binds to protein. The combination of torsion angles found in protein-bound forms is under-represented in ATP molecule in water. These findings suggest that ATP-binding protein exerts forces on ATP molecule to assume a conformation that is rarely found in solution, and that this conformation change should be a trigger for the reactions on ATP molecule. © 2013 The Biophysical Society of Japan.

Lysosomal β-galactosidase (β-Gal) deficiency causes a group of disorders that include neuronopathic GM1 gangliosidosis and non-neuronopathic Morquio B disease. We have previously proposed the use of small molecule ligands of β-Gal as pharmacological chaperones (PCs) for the treatment of GM1 gangliosidosis brain pathology. Although it is still under development, PC therapy has yielded promising preclinical results in several lysosomal diseases. In this study, we evaluated the effect of bicyclic 1-deoxygalactonojirimycin (DGJ) derivative of the sp2-iminosugar type, namely 5N,6S-(N′-butyliminomethylidene)-6-thio-1- deoxygalactonojirimycin (6S-NBI-DGJ), as a novel PC for human mutant β-Gal. In vitro, 6S-NBI-DGJ had the ability to inhibit the activity of human β-Gal in a competitive manner and was able to protect this enzyme from heat-induced degradation. Computational analysis supported that the rigid glycone bicyclic core of 6S-NBI-DGJ binds to the active site of the enzyme, with the aglycone N′-butyl substituent, in a precise E-orientation, located at a hydrophobic region nearby. Chaperone potential profiling indicated significant increases of enzyme activity in 24 of 88 β-Gal mutants, including four common mutations. Finally, oral administration of 6S-NBI-DGJ ameliorated the brain pathology of GM1 gangliosidosis model mice. These results suggest that 6S-NBI-DGJ is a novel PC that may be effective on a broad range of β-Gal mutants. Copyright © 2013, The American Society of Gene &amp
Cell Therapy.

Background: Lynch syndrome is a hereditary cancer predisposition syndrome caused by a mutation in one of the DNA mismatch repair (MMR) genes. About 24% of the mutations identified in Lynch syndrome are missense substitutions and the frequency of missense variants in MSH6 is the highest amongst these MMR genes. Because of this high frequency, the genetic testing was not effectively used in MSH6 so far. We, therefore, developed CoDP (Combination of the Different Properties), a bioinformatics tool to predict the impact of missense variants in MSH6.
Methods: We integrated the prediction results of three methods, namely MAPP, PolyPhen-2 and SIFT. Two other structural properties, namely solvent accessibility and the change in the number of heavy atoms of amino acids in the MSH6 protein, were further combined explicitly. MSH6 germline missense variants classified by their associated clinical and molecular data were used to fit the parameters for the logistic regression model and to assess the prediction. The performance of CoDP was compared with those of other conventional tools, namely MAPP, SIFT, PolyPhen-2 and PON-MMR.
Results: A total of 294 germline missense variants were collected from the variant databases and literature. Of them, 34 variants were available for the parameter training and the prediction performance test. We integrated the prediction results of MAPP, PolyPhen-2 and SIFT, and two other structural properties, namely solvent accessibility and the change in the number of heavy atoms of amino acids in the MSH6 protein, were further combined explicitly. Variants data classified by their associated clinical and molecular data were used to fit the parameters for the logistic regression model and to assess the prediction. The values of the positive predictive value (PPV), the negative predictive value (NPV), sensitivity, specificity and accuracy of the tools were compared on the whole data set. PPV of CoDP was 93.3% (14/15), NPV was 94.7% (18/19), specificity was 94.7% (18/19), sensitivity was 93.3% (14/15) and accuracy was 94.1% (32/34). Area under the curve of CoDP was 0.954, that of MAPP for MSH6 was 0.919, of SIFT was 0.864 and of PolyPhen-2 HumVar was 0.819. The power to distinguish between pathogenic and non-pathogenic variants of these methods was tested by Wilcoxon rank sum test (p &lt; 8.9 x 10(-6) for CoDP, p &lt; 3.3 x 10(-5) for MAPP, p &lt; 3.1 x 10(-4) for SIFT and p &lt; 1.2 x 10(-3) for PolyPhen-2 HumVar), and CoDP was shown to outperform other conventional methods.
Conclusion: In this paper, we provide a human curated data set for MSH6 missense variants, and CoDP, the prediction tool, which achieved better accuracy for predicting the impact of missense variants in MSH6 than any other known tools. CoDP is available at http://cib.cf.ocha.ac.jp/CoDP/.

Background: ORC binds to replication origins, but human ORC does not exhibit apparent sequence-specificity. Results: G-quadruplex (G4)-preferable RNA or single-stranded DNA competes for DNA binding of ORC. Conclusion: HumanORCbinds preferentially toRNAand single-strandedDNAthat form G4, and the certain domain in ORC1 is involved in this binding. Significance: This ability may correlate with the G4-formable motif in human replication origins. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.

The MSH6 gene is one of the mismatch repair genes involved in Lynch syndrome and its mutations account for 10-20% of Lynch syndrome. Although previous studies suggested that the difference of the geographical region affects the clinical phenotype of Lynch syndrome, there has been no report on the detailed features of Japanese Lynch syndrome patients carrying an MSH6 mutation. The aim of the present study was to investigate the clinical and molecular features of MSH6 mutation carriers in Japan. Surgically resected 1720 colorectal carcinoma specimens were screened by microsatellite instability (MSI) testing and the MSI-high cases were subjected to a germline mutation analysis of the mismatch repair genes MLH1, MSH2 and MSH6. We investigated the clinical and molecular features of the MSH6 variants, such as the family cancer history, pathological findings, immunohistochemistry, methylation status of the MLH1 promoter and BRAF mutation in the colorectal tumor. Furthermore, the impact of the missense variants on MSH6 protein was predicted by using in silico tools. We identified nine novel pathogenic mutations and eight unclassified missense variants. Among the eight missense variants, three were suspected pathogenic by in silico analysis. We also found that most colorectal cancers in the MSH6 mutation carrier were diagnosed after the age of 50 and were localized distally. Furthermore, the mean age at diagnosis of endometrial cancer in Japanese MSH6 mutation carriers (49.2 years) was earlier than previous reports from Western countries (56.5 years). These results may improve the surveillance program for Japanese MSH6 mutation carriers.

Protein is the major component of the organism. A hole (pocket) on the surface of a protein is known to be the best target for a drug to react. We started analyzing how 'drug ability' of proteins related to the locations amino acids in a pocket. This poster presents a visualization tool for a distance distribution analysis between two types of amino acids in a pocket and proposes the biological interpretation of the visualization results. © 2013 IEEE.

Competitive inhibitors of either α-galactosidase (α-Gal) or β-galactosidase (β-Gal) with high affinity and selectivity have been accessed by exploiting aglycone interactions with conformationally locked sp 2-iminosugars. Selected compounds were profiled as potent pharmacological chaperones for mutant lysosomal α- and β-Gal associated with Fabry disease and GM 1 gangliosidosis. © 2012 The Royal Society of Chemistry.

In comparative modeling, the quality of amino acid sequence alignment still constitutes a major bottleneck in the generation of high quality models of protein three-dimensional (3D) structures. Substantial efforts have been made to improve alignment quality by revising the substitution matrix, introducing multiple sequences, replacing dynamic programming with hidden Markov models, and incorporating 3D structure information. Improvements in the gap penalty have not been a major focus, however, following the development of the affine gap penalty and of the secondary structure dependent gap penalty. We revisited the correlation between protein 3D structure and gap location in a large protein 3D structure data set, and found that the frequency of gap locations approximated to an exponential function of the solvent accessibility of the inserted residues. The nonlinearity of the gap frequency as a function of accessibility corresponded well to the relationship between residue mutation pattern and residue accessibility. By introducing this relationship into the gap penalty calculation for pairwise alignment between template and target amino acid sequences, we were able to obtain a sequence alignment much closer to the structural alignment. The quality of the alignments was substantially improved on a pair of sequences with identity in the "twi-light zone&apos;&apos; between 20 and 40%. The relocation of gaps by our new method made a significant improvement in comparative modeling, exemplified here by the Bacillus subtilis yitF protein. The method was implemented in a computer program, ALAdeGAP (ALignment with Accessibility dependent GAp Penalty), which is available at http://cib.cf.ocha.ac.jp/target_protein/. Proteins 2011; 79:1868-1877. (C) 2011 Wiley-Liss, Inc.

「タンパク質の構造を決める」シリーズの第6回では，決定されたタンパク質の立体構造から機能を推定する方法について概観する．過去5回の解説では，タンパク質構造解析法の最前線が紹介されてきた．機能がすでによくわかっているタンパク質の立体構造を決定すると，そのタンパク質がどのように機能しているのかを化学的に理解することができるようになる．特に酵素の場合は，反応機構の詳細を明らかにできる．しかし近年，タンパク質の機能解析において，別のアプローチが登場してきた．ある生物種のゲノム全塩基配列を決定できるようになった結果，生物は新規のタンパク質をたくさんもっていることが明らかになった．このタンパク質がどのような機能をもっているのかを知るための手段のひとつとして，そのタンパク質の立体構造決定も行なわれている(構造ゲノミクス)．新規タンパク質の機能を立体構造から推定しようという試みである．これは今までにない新しいアプローチであり，立体構造から機能を推定する問題として，構造バイオインフォマティクス研究者による挑戦が続いている．ここでは，タンパク質の立体構造からどのようにして機能を推定するのか，そしてどこに困難な点があるのかを紹介する．

Motivation: Structural features at protein-protein interfaces can be studied to understand protein-protein interactions. It was noticed that in a dataset of 45 multimeric proteins the interface could either be described as. at against. at or protruding/interwound. In the latter, residues within one chain were surrounded by those in other chains, whereas in the former they were not.
Results: A simple method was developed that could distinguish between these two types with results that matched those made by a human annotator. Applying this automatic method to a large dataset of 888 structures, chains at interfaces were categorized as non-surrounded or surrounded. It was found that the surrounded set had a significantly lower folding tendency using a sequence based measure, than the non-surrounded set. This suggests that before complexation, surrounded chains are relatively unstable and may be involved in &apos;fly-casting&apos;. This is supported by the finding that terminal regions are overrepresented in the surrounded set.

Transcripts from mitochondrial and chloroplast DNA of land plants often undergo cytidine to uridine conversion-type RNA editing events. RESOPS is a newly built database that specializes in displaying RNA editing sites of land plant organelles on protein three-dimensional (3D) structures to help elucidate the mechanisms of RNA editing for gene expression regulation. RESOPS contains the following information: unedited and edited cDNA sequences with notes for the target nucleotides of RNA editing, conceptual translation from the edited cDNA sequence in pseudo-UniProt format, a list of proteins under the influence of RNA editing, multiple amino acid sequence alignments of edited proteins, the location of amino acid residues coded by codons under the influence of RNA editing in protein 3D structures and the statistics of biased distributions of the edited residues with respect to protein structures. Most of the data processing procedures are automated; hence, it is easy to keep abreast of updated genome and protein 3D structural data. In the RESOPS database, we clarified that the locations of residues switched by RNA editing are significantly biased to protein structural cores. The integration of different types of data in the database also help advance the understanding of RNA editing mechanisms. RESOPS is accessible at http://cib.cf.ocha.ac.jp/RNAEDITING/.

We have developed coliSNP, a database server (http://yayoi.kansai.jaea.go.jp/colisnp) that maps non-synonymous single nucleotide polymorphisms (nsSNPs) on the three-dimensional (3D) structure of proteins. Once a week, the SNP data from the dbSNP database and the protein structure data from the Protein Data Bank (PDB) are downloaded, and the correspondence of the two data sets is automatically tabulated in the coliSNP database. Given an amino acid sequence, protein name or PDB ID, the server will immediately provide known nsSNP information, including the amino acid mutation caused by the nsSNP, the solvent accessibility, the secondary structure and the flanking residues of the mutated residue in a single page. The position of the nsSNP within the amino acid sequence and on the 3D structure of the protein can also be observed. The database provides key information with which to judge whether an observed nsSNP critically affects protein function and/or stability. As far as we know, this is the only web-based nsSNP database that automatically compiles SNP and protein information in a concise manner.

DNA photolyase recognizes ultraviolet-damaged DNA and breaks improperly formed covalent bonds within the cyclobutane pyrimidine dimer by a light-activated electron transfer reaction between the flavin adenine dinucleotide, the electron donor, and cyclobutane pyrimidine dinner, the electron acceptor. Theoretical analysis of the electron-tunneling pathways of the DNA photolyase derived from Anacystis nidulans can reveal the active role of the protein environment in the electron transfer reaction. Here, we report the unexpectedly important role of the single methionine residue, Met-353, where busy trafficking of electron-tunneling currents is observed. The amino acid conservation pattern of Met-353 in the homologous sequences perfectly correlates with experimentally verified annotation as photolyases. The bioinformatics sequence analysis also suggests that the residue plays a pivotal role in biological function. Consistent findings from different disciplines of computational biology strongly suggest the pivotal role of Met-353 in the biological function of DNA photolyase.

Here we report the new features and improvements in our latest release of the H-Invitational Database (H-InvDB; http://www.h-invitational.jp/), a comprehensive annotation resource for human genes and transcripts. H-InvDB, originally developed as an integrated database of the human transcriptome based on extensive annotation of large sets of full-length cDNA (FLcDNA) clones, now provides annotation for 120 558 human mRNAs extracted from the International Nucleotide Sequence Databases (INSD), in addition to 54 978 human FLcDNAs, in the latest release H-InvDB_4.6. We mapped those human transcripts onto the human genome sequences (NCBI build 36.1) and determined 34 699 human gene clusters, which could define 34 057 (98.1%) protein-coding and 642 (1.9%) non-protein-coding loci; 858 (2.5%) transcribed loci overlapped with predicted pseudogenes. For all these transcripts and genes, we provide comprehensive annotation including gene structures, gene functions, alternative splicing variants, functional non-protein-coding RNAs, functional domains, predicted sub cellular localizations, metabolic pathways, predictions of protein 3D structure, mapping of SNPs and microsatellite repeat motifs, co-localization with orphan diseases, gene expression profiles, orthologous genes, proteinprotein interactions (PPI) and annotation for gene families. The current H-InvDB annotation resources consist of two main views: Transcript view and Locus view and eight sub-databases: the DiseaseInfo Viewer, H-ANGEL, the Clustering Viewer, G-integra, the TOPO Viewer, Evola, the PPI view and the Gene family/group.

Integrin, a membrane protein with a huge extracellular domain, participates in cell-cell and cell-extracellular-matrix interactions for metazoan. A group of integrins is known to perform a large-scale structural change when the protein is activated, but the activation mechanism and generality of the conformational change remain to be elucidated. We performed normal-mode analysis of the elastic network model on integrin alpha(V)beta(3) ectodomain in the bent form and identified key residues that influenced molecular motions. Iterative normal-mode calculations demonstrated that the specific nonbonded interactions involving the key residues work as a snap to keep integrin in the bent form. The importance of the key residues for the conformational change was further verified by mutation experiments, in which integrin alpha(IIb)beta(3) was used. The conservation pattern of amino acid residues among the integrin family showed that the characteristic pattern of residues seen around these key residues is found in the limited groups of integrin beta-chains. This conservation pattern suggests that the molecular mechanism of the conformational change relying on the interactions found in integrin alpha(V)beta(3) is unique to the limited types of integrins.

Background: In plant organelles, specific messenger RNAs (mRNAs) are subjected to conversion editing, a process that often converts the first or second nucleotide of a codon and hence the encoded amino acid. No systematic patterns in converted sites were found on mRNAs, and the converted sites rarely encoded residues located at the active sites of proteins. The role and origin of RNA editing in plant organelles remain to be elucidated.
Results: Here we study the relationship between amino acid residues encoded by edited codons and the structural characteristics of these residues within proteins, e. g., in protein-protein interfaces, elements of secondary structure, or protein structural cores. We find that the residues encoded by edited codons are significantly biased toward involvement in helices and protein structural cores. RNA editing can convert codons for hydrophilic to hydrophobic amino acids. Hence, only the edited form of an mRNA can be translated into a polypeptide with helix-preferring and core-forming residues at the appropriate positions, which is often required for a protein to form a functional three-dimensional (3D) structure.
Conclusion: We have performed a novel analysis of the location of residues affected by RNA editing in proteins in plant organelles. This study documents that RNA editing sites are often found in positions important for 3D structure formation. Without RNA editing, protein folding will not occur properly, thus affecting gene expression. We suggest that RNA editing may have conferring evolutionary advantage by acting as a mechanism to reduce susceptibility to DNA damage by allowing the increase in GC content in DNA while maintaining RNA codons essential to encode residues required for protein folding and activity.

RNA editing in land plant organelles is a process primarily involving the conversion of cytidine to uridine in pre-mRNAs. The process is required for gene expression in plant organelles, because this conversion alters the encoded amino acid residues and improves the sequence identity to homologous proteins. A recent study uncovered that proteins encoded in the nuclear genome are essential for editing site recognition in chloroplasts; the mechanisms by which this recognition occurs remain unclear. To understand these mechanisms, we determined the genomic and cDNA sequences of moss Takakia lepidozioides chloroplast genes, then computationally analyzed the sequences within -30 to +10 nucleotides of RNA editing sites (neighbor sequences) likely to be recognized by trans-factors. As the T lepidozioides chloroplast has many RNA editing sites, the analysis of these sequences provides a unique opportunity to perform statistical analyses of chloroplast RNA editing sites. We divided the 302 obtained neighbor sequences into eight groups based on sequence similarity to identify group-specific patterns. The patterns were then applied to predict novel RNA editing sites in T. lepidozioides transcripts; similar to 60% of these predicted sites are true editing sites. The success of this prediction algorithm suggests that the obtained patterns are indicative of key sites recognized by trans-factors around editing sites of T. lepidozioides chloroplast genes.

A vast amount of DNA sequence data, protein three-dimensional (3D) structure data, and RNA expression data have been produced by the efforts of genome sequencing, structural genomics, and omics projects, and we are at the stage where comprehensive views of cell activity and molecular mechanisms of life can be deduced. But in reality, we are inundated with massive amounts of data and are still in the process of finding ways to fully utilize the data. In this report, I would like to present our observations on the growth of protein 3D structure data and our effort to deduce the functions from the 3D structures. We found that the 3D structure of quite a high proportion of proteins derived from genome sequences can be now predicted and methods to predict the functions from 3D structures are in high demand. The methods we have developed can be used to predict some functions, namely RNA and ligand interfaces, based on those 3D structures and DNA sequences with relatively high accuracy. The methods enable predictions that are accurate enough to help with deducing the atomic structures of the complexes.

The emerging grid computing technologies enable bioinformatics scientists to conduct their researches in a virtual laboratory, in which they share public databases, computational tools as well as their analysis workflows. However, the development of grid applications is still a nightmare for general bioinformatics scientists, due to the lack of grid programming environments, standards and high-level services. Here, we present a system, which we named Bioinformatics: Ask Any Questions (BAAQ), to automate this development procedure as much as possible. BAAQ allows scientists to store and manage remote biological data and programs, to build analysis workflows that integrate these resources seam-lessly, and to discover knowledge from available resources. This paper addresses two issues in building grid applications in bioinformatics: how to smoothly compose an analysis workflow using heterogeneous resources and how to efficiently discover and re-use available resources in the grid community. Correspondingly an intelligent grid programming environment and an active solution recommendation service are proposed. Finally, we present a case study applying BAAQ to a bioinformatics problem.

Genome sequencing and structural genomics projects are both proceeded to gain a new perspective of life, that is global views on mechanisms of life with comprehensive and unbiased fashion. We now have genome sequences of human and other species, and are going to have a three-dimensional structure of whole proteins. Those massive pieces of information can only be deciphered with collaboration of computational biology. In this paper, we will discuss the amount of data we have at the moment and one of the new views on mechanisms of cellular function regulation obtained based on the computational analyses of those data.

In silico bioinformatics experiments involve integration of and access to computational tools and biological databases. The emerging grid computing technologies enable bioinformatics scientists to conduct their researches in a virtual laboratory, in which they share public databases, computational tools as well as their analysis workflows. However, the development of grid applications is still a nightmare for general bioinformatics scientists, due to the lack of grid programming environments, standards and high-level services. Here, we present a system, which we named Bioinformatics: Ask Any Questions (BAAQ), to automate this development procedure as much as possible. BAAQ allows scientists to store and manage remote biological data and program resources, to build analysis workflows that integrate these resources seamlessly, and to discover knowledge from available resources. This paper addresses two issues in building grid applications in bioinformatics: how to smoothly compose an analysis workflow using heterogeneous resources and how to efficiently discover and re-use available resources in the grid community. Correspondingly an intelligent grid programming environment and an active solution recommendation service are proposed. Finally, we present a case study applying BAAQ to a bioinformatics problem. © 2006, Australian Computer Society, Inc.

We have cloned, sequenced, and characterized cDNA of actins from five ciliate species of three different classes of the phylum Ciliophora: Karyorelictea (Loxodes striatus), Heterotrichea (Blepharisma japonicum, Blepharisma musculus), and Litostomatea (Didinium nasutum, Dileptus margaritifer). Loxodes striatus uses UGA as the stop codon and has numerous in-frame UAA and UAG, which are translated into glutamine. The other four species use UAA as the stop codon and have no in-frame UAG nor UGA. The putative amino acid sequences of the newly determined actin genes were found to be highly divergent as expected from previous findings of other ciliate actins. These sequences were also highly divergent from other ciliate actins, indicating that actin genes are highly diverse even within the phylum Ciliophora. Phylogenetic analysis showed high evolutionary rate of ciliate actins. Our results suggest that the evolutionary rate was accelerated because of the differences in molecular interactions.

The genomes of more than 100 species have been sequenced, and the biological functions of encoded proteins are now actively being researched. Protein function is based on interactions between proteins and other molecules. One approach to assuming protein function based on genomic sequence is to predict interactions between an encoded protein and other molecules. As a data source for such predictions, knowledge regarding known protein-small molecule interactions needs to be compiled. We have, therefore, surveyed interactions between proteins and other molecules in Protein Data Bank (PDB), the protein three-dimensional (3D) structure database. Among 20,685 entries in PDB (April, 2003), 4,189 types of small molecules were found to interact with proteins. Biologically relevant small molecules most often found in PDB were metal ions, such as calcium, zinc, and magnesium. Sugars and nucleotides were the next most common. These molecules are known to act as cofactors for enzymes and/or stabilizers of proteins. In each case of interactions between a protein and small molecule, we found preferred amino acid residues at the interaction sites. These preferences can be the basis for predicting protein function from genomic sequence and protein 3D structures. The data pertaining to these small molecules were collected in a database named Het-PDB Navi., which is freely available at http:// daisy.nagahama-i-bio.ac.jp/golab/hetpdbnavi.html and linked to the official PDB home page.

The catalytic domain of xylanases belonging to glycoside hydrolase family 10 ( GH10) can be divided into 22 modules (M1 to M22; Sato, Y., Niimura, Y., Yura, K., and Go, M. ( 1999) Gene (Amst.) 238, 93 - 101). Inspection of the crystal structure of a GH10 xylanase from Streptomyces olivaceoviridis E-86 (SoXyn10A) revealed that the catalytic domain of GH10 xylanases can be dissected into two parts, an N-terminal larger region and C-terminal smaller region, by the substrate binding cleft, corresponding to the module border between M14 and M15. It has been suggested that the topology of the substrate binding clefts of GH10 xylanases are not conserved (Charnock, S. J., Spurway, T. D., Xie, H., Beylot, M. H., Virden, R., Warren, R. A. J., Hazlewood, G. P., and Gilbert, H. J. ( 1998) J. Biol. Chem. 273, 32187 - 32199). To facilitate a greater understanding of the structure-function relationship of the substrate binding cleft of GH10 xylanases, a chimeric xylanase between SoXyn10A and Xyn10A from Cellulomonas fimi (CfXyn10A) was constructed, and the topology of the hybrid substrate binding cleft established. At the three-dimensional level, SoXyn10A and CfXyn10A appear to possess 5 subsites, with the amino acid residues comprising subsites -3 to +1 being well conserved, although the +2 subsites are quite different. Biochemical analyses of the chimeric enzyme along with SoXyn10A and CfXyn10A indicated that differences in the structure of subsite +2 influence bond cleavage frequencies and the catalytic efficiency of xylooligosaccharide hydrolysis. The hybrid enzyme constructed in this study displays fascinating biochemistry, with an interesting combination of properties from the parent enzymes, resulting in a low production of xylose.

The human genome sequence defines our inherent biological potential
the realization of the biology encoded therein requires knowledge of the function of each gene. Currently, our knowledge in this area is still limited. Several lines of investigation have been used to elucidate the structure and function of the genes in the human genome. Even so, gene prediction remains a difficult task, as the varieties of transcripts of a gene may vary to a great extent. We thus performed an exhaustive integrative characterization of 41,118 full-length cDNAs that capture the gene transcripts as complete functional cassettes, providing an unequivocal report of structural and functional diversity at the gene level. Our international collaboration has validated 21,037 human gene candidates by analysis of high-quality full-length cDNA clones through curation using unified criteria. This led to the identification of 5,155 new gene candidates. It also manifested the most reliable way to control the quality of the cDNA clones. We have developed a human gene database, called the H-Invitational Database (H-InvDB
http://www.h-invitational.jp/). It provides the following: integrative annotation of human genes, description of gene structures, details of novel alternative splicing isoforms, non-protein-coding RNAs, functional domains, subcellular localizations, metabolic pathways, predictions of protein three-dimensional structure, mapping of known single nucleotide polymorphisms (SNPs), identification of polymorphic microsatellite repeats within human genes, and comparative results with mouse full-length cDNAs. The H-InvDB analysis has shown that up to 4% of the human genome sequence (National Center for Biotechnology Information build 34 assembly) may contain misassembled or missing regions. We found that 6.5% of the human gene candidates (1,377 loci) did not have a good protein-coding open reading frame, of which 296 loci are strong candidates for non-protein-coding RNA genes. In addition, among 72,027 uniquely mapped SNPs and insertions/deletions localized within human genes, 13,215 nonsynonymous SNPs, 315 nonsense SNPs, and 452 indels occurred in coding regions. Together with 25 polymorphic microsatellite repeats present in coding regions, they may alter protein structure, causing phenotypic effects or resulting in disease. The H-InvDB platform represents a substantial contribution to resources needed for the exploration of human biology and pathology.

To facilitate an understanding of structure-function relationships, chimeric xylanases were constructed by module shuffling between the catalytic domains of the FXYN from Streptomyces olivaceoviridis E-86 and the Cex from Cellulomonas fimi. In the family F/10 xylanases, the modules M4 and M5 relate to substrate binding so that modules M4 and M5 of the FXYN were replaced with those of the Cex and the chimeric enzymes denoted FCF-C4, FCF-C5 and FCF-C4,5 were constructed. The kcat value of FCF-C5 for p-nitrophenyl-β-D-cellobioside was similar to that of the FXYN (2.2 s-1)
however, the kcat value of FCF-C4 for p-nitrophenyl-β-D-cellobioside was significantly higher (7.0 s-1). The loss of the hydrogen bond between E46 and S22 or the presence of the I49W mutation would be expected to change the position of Q88, which plays a pivotal role in discriminating between glucose and xylose, resulting in the increased kcat value observed for FCF-C4 acting on p-nitrophenyl-β-D-cellobioside since module M4 directly interacts with Q88. To investigate the synergistic effects of the different modules, module M10 of the FCF-C4 chimera was replaced with that of the Cex. The effects of replacement of module M4 and M10 were almost additive with regard to the Km and kcat values.

Eukaryotic genes encoding proteins are split by introns. Introns do not have information of protein amino acid sequences and they are spliced out during maturation of mRNA. Only exons are translated into proteins. Exon shuffling mediated by introns has been hypothesized as a molecular mechanism to shuffle protein segments, creating new functional proteins during evolution. We have shown that intron positions are correlated with module boundaries. A module is a small compact structural unit of a globular protein. As expected from the module-intron correlation, shuffling of a phosphate-binding module among DNA manipulating proteins was observed. Based on a compact conformation of a module, we expected mechanical stability of a single module. Molecular dynamics studies indeed show that a single module of barnase has mechanical stability. Such stability of a single module, together with the correlation between module boundaries and intron positions, implies that modules were combined into globular domains through exon shuffling during genome evolution. To investigate a role of module in protein folding, we designed a mini-protein by deleting one module from barnase and we could show conformational stability of the mini-barnase. The module engineering in barnase implies an independent behavior of the local region corresponding to a module on protein conformation. Hypothetical role of modules in folding process is also discussed.

Although the amino acid homology in the catalytic domain of FXYN xylanase from Streptomyces olivaceoviridis E-86 and Cex xylanase from Cellulomonas fimi is only 50%, an active chimeric enzyme was obtained by replacing module 10 in FXYN with module 10 from Cex, In the family F/10 xylanases, module 10 is an important region as it includes an acid/base catalyst and a substrate binding residue. In FXYN, module 10 consists of 15 amino acid residues, while in Cex it consists of 14 amino acid residues. The K-m and k(cat) values of the chimeric xylanase FCF-C10 for PKP-xylobioside (PNP-X-2) were 10-fold less than those for FXYN, CD spectral data indicated that the structure of the chimeric enzyme was similar to that of FXYN, Based on the comparison of the amino acid sequences of FXYN and Cex in module 10, we constructed four mutants of FXYN, When D133 or S135 of FXYN,vas deleted, the kinetic properties were not changed from those of FXYN. By deletion of both D133 and S135, the K-m value for PNP-X-2 decreased from the 2.0 mM of FXYN to 0.6 mM and the k(cat) value decreased from the 20 s(-1) of FXYN to 8.7 s(-1). Insertion of Q140 into the doubly deleted mutant further reduced the K-m value to 0.3 mM and the k(cat) value to 3.8 s(-1). These values are close to those for the chimeric enzyme FCF-C10, These results indicate that module 10 itself is able to accommodate changes in the sequence position of amino acids which are critical for enzyme function, Since changes of the spatial position of these amino acids would be expected to result in enzyme inactivation, module 10 must have some flexibility in its tertiary structure. The structure of module 10 itself also affects the substrate specificity of the enzyme. (C) 1999 Federation of European Biochemical Societies.

Helix–turn–helix motif is one of the common motifs observed in DNA-binding proteins. The motif interacts with DNA double helix and recognizes specific base sequences. It is assumed that the helix–turn–helix motif appears only once in seven prokaryotic transcriptional repressors of which 3-D structures have been determined by X-ray crystallographk studies. These prokaryotic repressors consist of several a-helices connected with turns. We report here that these repressors are decomposable into helix–turn–helix modules and their connectors. A module is defined as a compact structural unit with consecutive amino acid residues in a globular protein. Each of the helix- turn -helix motifs in the seven proteins corresponds approximately to a single helix-turn—helix module consisting of approximately 13 amino acids. Identification of modules of seven prokaryotic repressors and comparisons of then tertiary structures led to the conclusion that three of these DNA-binding proteins contain more than one helix–turn–helix module with a structure similar to the helix-turn-heUx motif. The difference in module organization of these DNA-binding proteins paves the way for further classification of the DNA-binding proteins with the helix- turn -helix motif. The structural repertoire of these transcriptional regulators was increased through different utilizations in the number of helix–turn–helix and other modules. The difference in DNA base recognition ability in these helix–turn–helix modules is ascribed to a difference in size of a side chain at the fifth residue from Gly, on the turn. © 1993, Oxford University Press.