The Treponema denticola surface
protease complex, consisting of PrtP
protease (
dentilisin) and two auxiliary
polypeptides (PrcA1 and PrcA2), is believed to contribute to
periodontal disease by degrading extracellular matrix components and disrupting host intercellular signaling. Previously, we showed that transcription of the
protease operon initiates upstream of TDE0760 (herein designated prcB), the open reading frame immediately 5' of prcA-prtP. The prcB gene is conserved in T. denticola strains. PrcB localizes to the
detergent phase of
Triton X-114 cell surface extracts and migrates as a 22-kDa
polypeptide, in contrast to the predicted 17-kDa cytoplasmic
protein encoded in the annotated T. denticola genome. Consistent with this observation, the PrcB N terminus is unavailable for Edman sequencing, suggesting that it is acylated. Nonpolar deletion of prcB in T. denticola showed that PrcB is required for production of PrtP
protease activity, including native PrtP cleavage of PrcA to PrcA1 and PrcA2. A 6xHis-tagged PrcB
protein coimmunoprecipitates with native PrtP, using either anti-PrtP or anti-His-tag
antibodies, and recombinant PrtP copurifies with PrcB-6xHis in
nickel affinity chromatography. Taken together, these data are consistent with identification of PrcB as a PrtP-binding
lipoprotein that likely stabilizes the PrtP
polypeptide during localization to the outer membrane.