Abstract
Porphyromonas gingivalis, a gram-negative obligate anaerobic bacterium, is considered to be a key pathogen in periodontal disease. The bacterium expresses Mfa1 fimbriae, which are composed of polymers of Mfa1. The minor accessory components Mfa3, Mfa4, and Mfa5 are incorporated into these fimbriae. In this study, we characterized Mfa4 using genetically modified strains. Deficiency in the mfa4 gene decreased, but did not eliminate, expression of Mfa1 fimbriae. However, Mfa3 and Mfa5 were not incorporated because of defects in posttranslational processing and leakage into the culture supernatant, respectively. Furthermore, the mfa4-deficient mutant had an increased tendency to auto-aggregate and form biofilms, reminiscent of a mutant completely lacking Mfa1. Notably, complementation of mfa4 restored expression of structurally intact and functional Mfa1 fimbriae. Taken together, these results indicate that the accessory proteins Mfa3, Mfa4, and Mfa5 are necessary for assembly of Mfa1 fimbriae and regulation of auto-aggregation and biofilm formation of P. gingivalis. In addition, we found that Mfa3 and Mfa4 are processed to maturity by the same RgpA/B protease that processes Mfa1 subunits prior to polymerization.
Highlights
Porphyromonas gingivalis, a gram-negative obligate anaerobic bacterium, is a component of dental plaque biofilms in humans and plays a key role in the initiation and progression of chronic periodontitis [1]
Complementation of mfa4 restored expression of structurally intact and functional Mfa1 fimbriae. These results indicate that the accessory proteins Mfa3, Mfa4, and Mfa5 are necessary for assembly of Mfa1 fimbriae and regulation of auto-aggregation and biofilm formation of P. gingivalis
Mfa4 is one of the accessory proteins incorporated into Mfa1 fimbriae [12, 13], but its role has remained unclear
Summary
Porphyromonas gingivalis, a gram-negative obligate anaerobic bacterium, is a component of dental plaque biofilms in humans and plays a key role in the initiation and progression of chronic periodontitis [1]. The organism expresses a number of potential virulence factors, including fimbriae and gingipain. Role of Accessory Protein Mfa in Mfa Fimbriae proteases [5]. The type strain of P. gingivalis, ATCC 33277, expresses two forms of fimbriae, FimA and Mfa, which are composed mostly of polymers of the corresponding proteins [6], and facilitate binding to host cells, matrix proteins, and other bacteria. Gingipains are a family of proteolytic enzymes that comprises arginine-specific (RgpA and RgpB) and lysine-specific (Kgp) proteases, and participates in a wide range of pathological and physiological processes [7]
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