Molecular genetics and nomenclature of proteases of Porphyromonas gingivalis

The strategies used by bacterial pathogens to establish and maintain themselves in the host represent one of the fundamental aspects of microbial pathogenesis. Characterization of these strategies and the underlying molecular machinery offers new opportunities both to our understanding of how organisms cause disease in susceptible individuals and to the development of novel therapeutic measures designed to undermine or interfere with these determinants of successful survival. With respect to the microbial aetiology of the periodontal diseases, a growing body of evidence suggests that the proteolytic enzymes of Porphyromonas gingivalis represent key survival and, by extrapolation, virulence determinants of this periodontal bacterium. This in turn has led to international efforts to characterize these enzymes at the gene and protein level. Approximately 20 protease genes of P. gingivalis with different names and accession numbers have been deposited in the gene databases and a correspondingly heterogeneous nomenclature system is employed for the products of these genes in the literature. However, it is evident, through comparison of these gene sequences and through gene inactivation studies, that the genetic structure of the proteases of this organism, particularly those with specificity for arginyl and lysyl peptide bonds, is less complicated than originally thought. The major extracellular and surface associated arginine specific protease activity is encoded by 2 genes which we recommend be designated rgpA and rgpB (arg-gingipains A & B). Similarly we recommend that the gene encoding the major lysine specific protease activity is designated kgp (lys-gingipain). These three genes, which account for all the extracellular/surface arginine and lysine protease activity in P. gingivalis, belong to a family of sequence-related proteases and haemagglutinins.