Characterization and cDNA cloning of a platelet aggregation inhibitor

A novel platelet aggregation inhibitor, sal-C, was purified to homogeneity from the venom of Korean snake (Agkistrodon halys brevicaudus). Several lin es of experimental evidence clearly indicated that sal-C inhibits not only the collagen-induced platelet aggregation, but also the aggregation mediate d by the cell surface glycoprotein IIb-IIIa (GP IIb-IIIa), We have isolated the cDNA encoding sal-C from the cDNA library of the snake venom gland and analyzed its complete nucleotide sequence, Sal-C is' a single-chain polype ptide composed of 212 amino acids including 24 cysteines, The deduced polyp eptide sequence of sal-C demonstrated considerable homology to previously d escribed protein species of the collagen-induced platelet aggregation inhib itor family Sal-C does not have the Arg-Gly-Asp (RGD) motif, but contains t he Ser-Glu-Cys-Asp sequence. Interestingly, sal-C was found to inhibit GP I Ib-IIIa binding td immobilized fibrinogen which is antagonized by the typic al RGD moth of disintegrins.