The opdB Locus Encodes the Trypsin-Like Peptidase Activity of Treponema denticola

Abstract

ABSTRACT High levels of Treponema denticola in subgingival dental plaque are associated with severe periodontal disease. T. denticola , along with Porphyromonas gingivalis and Bacteroides forsythus , are the only cultivatable oral microorganisms that produce significant amounts of “trypsin-like” peptidase activity. The ability of subgingival plaque to hydrolyze N -α-benzoyl- dl -arginine-2-naphthylamide (BANA) is associated with high levels of one or more of these organisms. The purpose of this study was to identify the gene encoding trypsin-like activity in T. denticola and thus facilitate molecular-level studies of its potential role in disease. Using published peptide sequences of a T. denticola surface-associated oligopeptidase with BANA-hydrolyzing activity, we identified the gene, designated opdB , in an apparently noncoding region of the T. denticola genome unannotated contigs (11/2000; http://www.tigr.org ). The opdB gene begins with a TTG start codon and encodes a 685-residue peptide with high homology to the oligopeptidase B family in prokaryotes and eukaryotes. An isogenic T. denticola opdB mutant was constructed by allelic replacement mutagenesis using an ermF/AM gene cassette. The mutant lacked BANA-hydrolyzing activity and had a slightly slower growth rate than the parent strain. This mutant will be used in future studies of interactions of T. denticola with host cells and tissue.