Identification of functional domains of the minor fimbrial antigen involved in the interaction of Porphyromonas gingivalis with oral streptococci

AbstractPorphyromonas gingivalis is associated with chronic periodontitis and may initially colonize the oral cavity by adhering to streptococci. Adhesion to streptococci is driven by interaction of the minor fimbrial antigen (Mfa1) with streptococcal antigen I/II. We identified the region of antigen I/II required for this interaction and developed small molecule mimetics that inhibitedP. gingivalis adherence. However, the functional motifs of Mfa1 involved in the interaction with antigen I/II remain uncharacterized. A series of N ‐ and C‐terminal peptide fragments of Mfa1 were expressed and tested for inhibition ofP. gingivalis adherence toS. gordonii. This approach identified residues 225 to 400 of Mfa1 as essential forP. gingivalis adherence. Using the three dimensional structure of Mfa1, a putative binding cleft was identified using SiteMap and five small molecule mimetics could dock in this site. Site specific mutation of residues in the predicted cleft, including R240A, W275A, D321A and A357P inhibited the interaction of Mfa1 with streptococci whereas mutation of residues not in the predicted cleft (V238A, I252F and ΔK253) had no effect. Complementation of an Mfa1‐deficientP. gingivalis strain with wild typemfa1 restored adherence to streptococci whereas complementation with full lengthmfa1 containing the R240A or A357P mutations did not restore adherence. The mutations did not affect polymerization of Mfa1, suggesting that the complemented strains produced intac...

Source: Molecular Oral Microbiology - January 27, 2020 Category: Microbiology Authors: Mohammad Roky, John O. Trent, Donald R. Demuth Tags: ORIGINAL ARTICLE Source Type: research