INTERACTION OF ECHICETIN WITH A HIGH-AFFINITY THROMBIN BINDING-SITE ON PLATELET GLYCOPROTEIN GPIB

Echicetin, a protein isolated from Echis carinatus snake venom, inhibi ted platelet aggregation and secretion induced by low concentrations o f thrombin (<0.2 U/ml), by binding to platelet glycoprotein Ib (GPIb). The inhibition was not observed when the platelets were stimulated wi th higher concentrations of thrombin (>0.2 U/ml). Echicetin competed w ith thrombin for binding to the high affinity site on GPIb. Thrombin a lso inhibited 50% of the binding of I-125-echicetin to the platelets.