Active site structure of a hemagglutinating protease from Porphyromonas gingivalis: similarity to clostripain

The active site of a 44-kDa hemagglutinating arginine-specific protease from the putative periodontopathogen Porphyromonas gingivalis was specifically labeled with N alpha-[3H]acetyllysine chloromethyl ketone. After enzymatic digestion of the labeled enzyme, a labeled active site peptide was isolated by HPLC. The sequence of the active site peptide was determined, after its treatment with NaBH4 to reduce the ketone group of the reagent moiety, to be Asp-Val-Ala-Cys-Val-Asn-Gly. The cysteine residue was found to be the site for labeling. The sequence resembled the active site structure of the arginine-specific cysteine protease clostripain from Clostridium histolyticum.