| Research Abstract |
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 progressive 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, and we found that the three ORFs had a significant similarity with FtsQ (16%), FtsA (33%), and FtsZ (54%) in E. coli, respectively. 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 properties 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-
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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.
Sequence comparison of the known prokaryotic FtsZs revealed that this region contained a highly conserved domain, designated A-domain, in which Ala320 of PgFtsZ was conserved throughout a broad variety of species. Therefore, we analyzed the role of Ala320 by site-directed mutagenesis. We found that overexpression of ZA320H and ZA320R resulted in the normal phenotype, unlike the wild type. These results suggested that Ala320 is highly conserved and is crucial for cell division. Since the A-domain was also conserved among other periodontopathogens, this work has implications that antibacterial agents for periodontal diseases targeted the A-domain could be developed in the near future. Less
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