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J. Bacteriol., May 1996, 2818-2824, Vol 178, No. 10
K Nakayama, F Yoshimura, T Kadowaki and K Yamamoto
Arginine-specific cysteine proteinase (Arg-gingipain [RGP], a major
proteinase secreted from the oral anaerobic bacterium Porphyromonas
gingivalis, is encoded by two separate genes (rgpA and rgpB) on the P.
gingivalis chromosome and widely implicated as an important virulence
factor in the pathogenesis of periodontal disease (K. Nakayama, T.
Kadowaki, K. Okamoto, and K. Yamamoto, J. Biol. Chem. 270:23619-23626,
1995). In this study, we investigated the role of RGP in the formation of
P. gingivalis fimbriae which are thought to mediate adhesion of the
organism to the oral surface by use of the rgp mutants. Electron
microscopic observation revealed that the rgpA rgpB double (RGP-null)
mutant possessed very few fimbriae on the cell surface, whereas the number
of fimbriae of the rgpA or rgpB mutant was similar to that of the wild-type
parent strain. The rgpB+ revertants that were isolated from the double
mutant and recovered 20 to 40% of RGP activity of the wild-type parent
possessed as many fimbriae as the wild-type parent, indicating that RGP
significantly contributes to the fimbriation of P. gingivalis as well as to
the degradation of various host proteins, disturbance of host defense
mechanisms, and hemagglutination. Immunoblot analysis of cell extracts of
these mutants with antifimbrilin antiserum revealed that the rgpA rgpB
double mutant produced small amounts of two immunoreactive proteins with
molecular masses of 45 and 43 kDa, corresponding to those of the precursor
and mature forms of fimbrilin, respectively. The result suggests that RGP
may function as a processing proteinase for fimbrilin maturation. In
addition, a precursor form of the 75-kDa protein, one of the major outer
membrane proteins of P. gingivalis, was accumulated in the rgpA rgpB double
mutant but not in the single mutants and the revertants, suggesting an
extensive role for RGP in the maturation of some of the cell surface
proteins.
Copyright © 1996, American Society for Microbiology
Involvement of arginine-specific cysteine proteinase (Arg-gingipain) in fimbriation of Porphyromonas gingivalis
Department of Microbiology, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. kojidef@mbox.nc.kyushu-u.ac.jp
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