CHARACTERIZATION, GENETIC-ANALYSIS, AND EXPRESSION OF A PROTEASE ANTIGEN (PRPRI) OF PORPHYROMONAS-GINGIVALIS W50

Previous studies of the serum immunoglobulin G antibody response of pe riodontal patients have demonstrated significant reactivity to a cell surface or extracellular arginine-specific protease of Porphyromonas g ingivalis which migrates as an similar to 50-kDa band on sodium dodecy l sulfate-polyacrylamide gels. In the present report, two forms of the enzyme (ArgI and ArgIA) with this electrophoretic behavior were isola ted. ArgI is a heterodimer of alpha and beta subunits, and ArgIA is a monomer composed of the catalytically active a component alone. The ge ne encoding ArgI (prpR1 encoding protease polyprotein ArgI) was cloned from Sau3AI digests of P. gingivalis W50 DNA into pUC18. Sequence ana lysis demonstrated that the alpha and beta components are contiguous o n the initial translation product and are flanked by large N- and C-te rminal extensions. prpR1 is 97.5% identical to the rgp-1 gene from P. gingivalis H66. prpR1 expression in Escherichia coli demonstrated the presence of an internal transcription-translation initiation site whic h could permit independent expression of different regions of the poly protein. Immunochemical analysis of P. gingivalis mid-logarithmic-phas e cultures suggested that the processing of PrpRI may be closely coupl ed to its synthesis, with only the final stages taking place at the ce ll surface, Southern hybridization studies demonstrated that the prpR1 gene is widely distributed in other P. gingivalis strains and that a second homologous locus to the alpha component and at least two other homologous loci to the beta component are present on the P. gingivalis chromosome. These data indicate that the ArgI protease of P. gingival is is a member of a family of sequence-related gene products which may share both functional and antigenic properties.