REGULATION OF PROTEASE EXPRESSION IN PORPHYROMONAS-GINGIVALIS

Although the strong protease activity of Porphyromonas gingivalis appe ars to be an important virulence property of these organisms, little i nformation is currently available regarding the regulation of expressi on of the multiple protease genes. Utilizing the lacZ reporter gene st rategy, the environmental factors which regulate the expression of the Arg-gingipain gene rgpA and the prtT protease gene were investigated. These two genes are reciprocally regulated since factors which retard ed growth (iron depletion and nutrient limitation) appeared to upregul ate rgpA expression while down-regulating prtT expression. However, in activation of the major rgpA gene resulted in increased transcription of the prtT and tpr protease genes while decreasing expression of the Lys-gingipain kgp gene as detected by Northern blot analysis. By contr ast, inactivation of the prtT gene did not significantly affect kgp ex pression but moderately decreased rgpA mRNA levels. These results indi cate that the protease genes of P. gingivalis are not coordinately reg ulated and suggest that some of these enzymes play specific roles in t he physiology and/or virulence of these organisms.