HEMOGLOBIN-BINDING PROTEIN PURIFIED FROM PORPHYROMONAS-GINGIVALIS IS IDENTICAL TO LYSINE-SPECIFIC CYSTEINE PROTEINASE (LYS-GINGIPAIN)

The functional protein that binds to human hemoglobin (hemoglobin-bind ing protein; HBP) was purified from Porphyromonas gingivalis cells. Th e analyses of the amino-terminal sequence and amino acid composition r evealed that HBP is identical to lysine-specific cysteine proteinase ( 51 kDa Lys-gingipain; KGP) of P. gingivalis 381. It is a novel finding that KGP has binding affinity to hemoglobin. The binding activity of HBP was enhanced by acidic or anaerobic conditions. Arg-gingipain, a m ember of the gingipain family, of P. gingivalis exhibited no ability t o bind to hemoglobin. The recombinant protein of KGP (r-KGP) generated in Escherichia coli showed both hemoglobin-binding and proteolytic ac tivities. The treatment of r-KGP by protein disulfide isomerase effect ively enhanced binding to hemoglobin, whereas the proteinase activity was decreased. The treated r-KGP significantly inhibited the binding o f hemoglobin to the whole cell extracts in a dose-dependent manner. Th ese results suggest that the hemoglobin binding of P. gingivalis is me diated by KGP through active domain(s) distinct from that for proteina se activity. (C) 1998 Academic Press.