PURIFICATION OF THE PORCINE PLATELET GP IIB-IIIA COMPLEX AND THE PROPOLYPEPTIDE OF VON-WILLEBRAND-FACTOR

Platelet membrane glycoproteins (GP) are involved in platelet adhesion and aggregation. The glycoprotein IIb-IIIa complex (GP IIb-IIIa) is a Ca2+-dependent heterodimer that binds fibrinogen and other adhesive p roteins, thereby mediating platelet aggregation and adhesion. We have purified two major glycoproteins from pig platelets by Concanavalin A- Sepharose, Heparin-Sepharose and Sephacryl S-300 HR chromatography (Fi tzgerald et al, Anal Biochem, 1985): i) the GP IIb-IIIa complex, GP II b Mr = 140,000 and GP IIIa a single chain of Mr = 95,000-100,000; and ii) a predominant glycoprotein of high molecular weight, the propolype ptide of von Willebrand factor (Mr = 80,000-100,000). Western-blot ana lysis of the purified GP IIb-IIIa showed that only certain monoclonal antibodies against the human receptor specifically recognize the porci ne complex. Differences between the porcine and human GP IIb-IIIa glyc oproteins could partially explain the decreased inhibitory effects of GP IIb/IIIa-antagonists (against the human receptor) in porcine platel ets.