Platelet Glycoprotein IIb-IIIa Protein Antagonists from Snake Venoms: Evidence for a Family of Platelet-Aggregation Inhibitors

The purification, complete amino acid sequence, and biological activity are described for several homologous snake venom proteins that are platelet glycoprotein (GP) IIb-IIIa antagonists and potent inhibitors of platelet aggregation. The primary structures of kistrin (from Agkistrodon rhodostoma), b...

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Veröffentlicht in:Proceedings of the National Academy of Sciences - PNAS 1990-04, Vol.87 (7), p.2471-2475
Hauptverfasser: Dennis, Mark S., Henzel, William J., Pitti, Robert M., Lipari, Michael T., Napier, Mary A., Deisher, Theresa A., Bunting, Stuart, Lazarus, Robert A.
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Sprache:eng
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Zusammenfassung:The purification, complete amino acid sequence, and biological activity are described for several homologous snake venom proteins that are platelet glycoprotein (GP) IIb-IIIa antagonists and potent inhibitors of platelet aggregation. The primary structures of kistrin (from Agkistrodon rhodostoma), bitan (from Bitis arietans), three isoforms of trigramin (from Trimeresusus gramineus), and an isoform of echistain (from Echis carinatus) were determined by automated sequence analysis and fast atom bombardment mass spectrometry analysis. Each of the proteins in this family, which range from 47 to 83 residues, contains an Arg-Gly-Asp amino acid sequence found in protein ligands that binds to GPIIb-IIIa, a high (17 ± 1%) cysteine content conserved in the primary sequence, and a homologous N-terminal region absent only in the echistatin isoforms. Each protein directly inhibits the interaction of purified platelet GPIIb-IIIa to immobilized fibrinogen about 100 times more effectively than does the pentapeptide Gly-Arg-Gly-Asp-Ser;IC50values range from 1.1 to 3.0 nM. The IC50value for the inhibition of platelet aggregation, using human platelet-rich plasma stimulated with ADP, ranges from 110 to 550 nM for the various proteins, about 1000-fold more potent than Gly-Arg-Gly-Asp-Ser. Kistrin binds reversibly to both resting and ADP-activated human platelets with high affinity (Kd= 10.8 nM and 1.7 nM, respectively) and to purified GPIIb-IIIa with a lower affinity (Kd= ≈ 100 nM). Finally, kistrin injected at 1.0 mg/kg into rabbits reversibly inhibits platelet aggregation ex vivo over 30 min without induction of thrombocytopenia. We propose that these proteins are members of a general class of proteins found in the venom of pit vipers that inhibit platelet aggregation by antagonism of the GPIIb-IIIa-fibrinogen interaction and as such serve as potential antithrombotic agents.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.87.7.2471