| Co-Investigator(Kenkyū-buntansha) |
WACHI Masaaki Tokyo Institute of Technology, Associate Prof., 生命理工学部, 助教授 (90192822)
AKIFUSA Sumio Kyushu Dental College, Assistant Prof., 歯学部, 助手 (40295861)
ANSAI Toshihiro Kyushu Dental College, Associate Prof., 歯学部, 助教授 (80244789)
YAMAGISHI Jyun-ichi Dainippon Pharmaceutical Company., 主任研究員
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| Research Abstract |
Peptidoglycan is known to be a heteropolymer with a unique chemical structure and biological activity, and be essential for cell viability of bacteria. We have already isolated and sequenced a gene encoding the MurC protein from Porphyromonas gingivalis (PgMurC gene), an oral anaerobic rod-shaped bacterium implicated in progressiove periodontal disease. The MurC protein functions in peptidoglycan synthesis and catalyzes the first step in the biosynthesis of cell wall peptidoglycan. The region including PgMurC gene appeared to be highly similar with mra region in E.coli, which contains genes concerned with peptidoglycan synthesis, and have been shown to be tightly clustered forming an operon. Then, we have sequenced the neibouring region of PgMurC gene, and we found that the three ORFs had a significant similarity with FtsQ (16%), FtsA (33%), and FtsZ (54%) in E.coli, respectively. The predicted FtsA from P.gingivalis (PgFtsA) had five motifs for ATPase domain, belonging to the actin fa
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mily, as in the FtsA from E.coli. When PgFtsA was overexpressed in E.coli, cell division was inhibited and its morphology changed to long filamentous cells. Electron micrographs of these cells revealed that the formation of aggregated structures existed in the E.coli cytoplasm. On the other hand, the FtsZ from P.gingivalis (PgFtsZ) possessed the clear motifs for GTP binding and hydrolysis, and the purified PgFtsZ protein exhibited GTPase activity with the following propeties different from other known FtsZ proteins ; 1) Na^+ and K^+ ions inhibited its GTPase activity. 2) PgFtsZ exhibited its GTPase activity even without Mg^<2+>, and completely retained its activity with EDTA.Very recently, a series of mutants deleted from the C-teminus of PgFtsZ were generated, and the change of their morphology were observed. We found that the delta C-177 mutant, deleted 177 amino acid residues from C-terminus, changed to the normal cells. These results suggest that amino acid residues from T281 to E330 may be important for the functional role in PgFtsZ.In order to identify amino acid residues in the corresponding region, mutant PgFtsZ proteins are currently generated through the use of site-directed mutagenesis. Less
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