MOLECULAR-CLONING AND CHARACTERIZATION OF PORPHYROMONAS-GINGIVALIS LYSINE-SPECIFIC GINGIPAIN - A NEW MEMBER OF AN EMERGING FAMILY OF PATHOGENIC BACTERIAL CYSTEINE PROTEINASES

The proteinases of Porphyromonas gingivalis are key virulence factors in the etiology and progression of periodontal disease. Previous work in our laboratories resulted in the purification of arginine- and lysi ne-specific cysteine proteinases, designated gingipains, that consist of several tightly associated protein subunits. Recent characterizatio n of arginine-specific gingipain-1 (gingipain R1; RGP-1) revealed that the sequence is unique and that the protein subunits are initially tr anslated as a polyprotein encoding a proteinase domain and multiple ad hesin domains (Pavloff, N., Potempa, J., Pike, R. N., Prochazka, V., K iefer, M. C., Travis, J., and Parr, P. J. (1995) J. Biol. Chem. 270, 1 007-1010). We now show that the lysine-specific gingipain (gingipain K ; KGP) is also biosynthesized as a polyprotein precursor that contains a proteinase domain that is 22% homologous to the proteinase domain o f RGP-1 and multiple adhesin domains. This precursor is similarly proc essed at distinct sites to yield active KGP. The key catalytic residue s in the proteinase domain of KGP are identical to those found in RGP- 1, but there are significant differences elsewhere within this domain that likely contribute to the altered substrate specificity of KGP. In dependent expression of the proteinase domain in insect cells has show n that KGP does not require the presence of the adhesin domains for co rrect folding to confer proteolytic activity.