Okayama University of Science, Japan
Seiichi Katayama has completed his Ph.D. at the age of 32 years from Kagawa Medical School in Japan. He has been studying on an anaerobe, Clostridium perfringens. He learned genetic molecular bacteriology at Pasture Institute in France for about two years (1993 to 1995). He is an associate professorinthe department of life science, Okayama University of Science. He has published more than 37 papers in some journals.
Clostridium perfringens is a Gram-positive spore-forming anaerobic bacteriumanda pathogen causing gas gangrene and food poisoning. Gas gangrene is mainly caused by -toxin (phospholipase C) produced by C.perfringens. Three phased A5-6-tracts (–66 to –40) lie upstream of the promoter for plc gene encoding the -toxin. The results of gel retardation assays and hydroxyl radical foot printings revealed that the subunit ofC. perfringens RNA polymerase binds to the minor grooves of the phased A-tracts through its C-terminal domain (CTD). The affinity of the subunit for the phased A-tracts wasestimated by surface plasmon resonance (SPR) [Kdwas 6.1 ( 0.3) 10−8 M]. To identify the amino acid residues involved in the binding of thesubunit to the phased A-tracts, 27 amino acids residues in theCTD were substituted with alanine. SPR analyses revealed that Arg261, Asn264, Gly292 and Lys294 in theCTD were critical for the binding to the phased A-tracts.The topology of these amino acid residues on the predicted structure of C. perfringensCTD indicated a contact path with the phased A-tracts that was similar to that of Escherichia coliCTD with the upstream (UP) element.SPR analyses at different temperatures (15, 25 and 37°C) indicated that the affinity of C. perfringens subunit for the phased A-tracts increased atlower temperatures, whereas that of E. coli subunit for UP element did not. These results suggested that the phased A-tracts directly enhanced the plc gene expression in a low-temperature-dependent manner.
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