Biomedical subjects

Takeshi Kawabata

Publications and source records attributed to Takeshi Kawabata.

4 recordsLinked to original sources

PubMed2003

MATRAS: A program for protein 3D structure comparison.

The recent accumulation of large amounts of 3D structural data warrants a sensitive and automatic method to compare and classify these structures. We developed a web server for comparing protein 3D structures using the program Matras (http://biunit.aist-nara.ac.jp/matras). An advantage of Matras is its structure similarity score, which is defined as the log-odds of the probabilities, similar to Dayhoff's substitution model of amino acids. This score is designed to detect evolutionarily related (homologous) structural similarities. Our web server has three main services. The first one is a pairwise 3D alignment, which is simply align two structures. A user can assign structures by either inputting PDB codes or by uploading PDB format files in the local machine. The second service is a multiple 3D alignment, which compares several protein structures. This program employs the progressive alignment algorithm, in which pairwise 3D alignments are assembled in the proper order. The third service is a 3D library search, which compares one query structure against a large number of library structures. We hope this server provides useful tools for insights into protein 3D structures.

Algorithms↗

PubMed2002

A systematic investigation identifies a significant number of probable pseudogenes in the Escherichia coli genome.

Pseudogenes are open reading frames (ORFs) encoding dysfunctional proteins with high homology to known protein-coding genes. Although pseudogenes were reported to exist in the genomes of many eukaryotes and bacteria, no systematic search for pseudogenes in the Escherichia coli genome has been carried out. Genome comparisons of E. coli strains K-12 and O157 revealed that many protein-coding sequences have prematurely terminated orthologs encoding unstable proteins. To systematically screen for pseudogenes, we selected ORFs generated by premature termination of the orthologous protein-coding genes and subsequently excluded those possibly arising from sequence errors. Lastly we eliminated those with close homologs in this and other species, as these shortened ORFs may actually have functions. The process produced 95 and 101 pseudogene candidates in K-12 and O157, respectively. The assigned three-dimensional structures suggest that most of the encoded proteins cannot fold properly and thus are dysfunctional, indicating that they are probably pseudogenes. Therefore, the existence of a significant number of probable pseudogenes in E. coli is predicted, awaiting experimental verification. Most of them were found to be genes with paralogs or horizontally transferred genes or both. We suggest that pseudogenes constitute a small fraction of the genomes of free-living bacteria in general, reflecting the faster elimination than production of pseudogenes.

Amino Acid Sequence↗

PubMed2002

GTOP: a database of protein structures predicted from genome sequences.

Large-scale genome projects generate an unprecedented number of protein sequences, most of them are experimentally uncharacterized. Predicting the 3D structures of sequences provides important clues as to their functions. We constructed the Genomes TO Protein structures and functions (GTOP) database, containing protein fold predictions of a huge number of sequences. Predictions are mainly carried out with the homology search program PSI-BLAST, currently the most popular among high-sensitivity profile search methods. GTOP also includes the results of other analyses, e.g. homology and motif search, detection of transmembrane helices and repetitive sequences. We have completed analyzing the sequences of 41 organisms, with the number of proteins exceeding 120 000 in total. GTOP uses a graphical viewer to present the analytical results of each ORF in one page in a 'color-bar' format. The assigned 3D structures are presented by Chime plug-in or RasMol. The binding sites of ligands are also included, providing functional information. The GTOP server is available at http://spock.genes.nig.ac.jp/~genome/gtop.html.

Amino Acid Motifs↗

PubMed2001

Solution structure of the fibronectin type III domain from Bacillus circulans WL-12 chitinase A1.

Growing evidence suggests that horizontal gene transfer plays an integral role in the evolution of bacterial genomes. One of the debated examples of horizontal gene transfer from animal to prokaryote is the fibronectin type III domain (FnIIID). Certain extracellular proteins of soil bacteria contain an unusual cluster of FnIIIDs, which show sequence similarity to those of animals and are likely to have been acquired horizontally from animals. Here we report the solution structure of the FnIIID of chitinase A1 from Bacillus circulans WL-12. To the best of our knowledge, this is the first tertiary structure to be reported for an FnIIID from a bacterial protein. The structure of the domain shows significant similarity to FnIIIDs from animal proteins. Sequence comparisons with FnIIIDs from other soil bacteria proteins show that the core-forming residues are highly conserved and, thus, are under strong evolutionary pressure. Striking similarities in the tertiary structures of bacterial FnIIIDs and their mammalian counterparts may support the hypothesis that the evolution of the FnIIID in bacterial carbohydrases occurred horizontally. The total lack of surface-exposed aromatic residues also suggests that the role of this FnIIID is different from those of other bacterial beta-sandwich domains, which function as carbohydrate-binding modules.

Amino Acid Sequence↗