Peptide inhibitors of Porphyromonas gingivalis colonization of dental plaque

Objectives: To develop peptides that inhibit Porphyromonas gingivalis colonization and biofilm formation.

Methods: We previously showed that a synthetic peptide (BAR) derived from streptococcal antigen I/II interacts with the minor fimbrial protein (Mfa) and is a potent inhibitor of P. gingivalis adherence and biofilm formation. A combinatorial approach coupled with circular dichroism spectroscopy and site specific mutagenesis was utilized to define the structural features of BAR contributing to its activity. These data were used to develop new peptides with increased activity.

Results: Substituting Arg for Asn¹¹⁸² and Ile for Val¹¹⁸⁵ in the NITVK active site of BAR resulted in a 2.5-fold increase in anti-biofilm activity. Circular dichroism spectroscopy indicated that it possessed greater a-helical content than BAR (28% vs. ~9%). To correlate a-helical content with inhibitory activity, a conformationally constrained analog of BAR with high a-helicity was synthesized. However, this peptide was a poor inhibitor of biofilm formation. Re-examination of the BAR sequence identified a second motif (VQDLL) that resembled the nuclear receptor box protein-protein interaction domain of eukaryotes. This region had been altered to synthesize the conformationally constrained peptide. The VQDLL and NITVK motifs in isolation did not inhibit P. gingivalis biofilms but rejoining the two motifs in a single 20-mer peptide restored biofilm inhibitory activity. Amino acid substitutions that altered the secondary structure of VQDLL, or that altered the positively charged Lys residues that flank VQDLL significantly reduced inhibitory activity.

Conclusions: These results show that the interacting interface of antigen I/II and Mfa encompasses both the VQDLL and NITVK motifs of antigen I/II and suggest that both must be considered in the design of potential therapeutic peptides or peptidomimetics that target P. gingivalis colonization and biofilm formation. Supported by RO1DE12505 from NIDCR