COnvulxin, a potent platelet-aggregating protein from Crotalus durissus terrificus venom, specifically binds to platelets

• Published in: Toxicon (Oxford) 1997-08, Vol.35 (8), p.1217-1228
• Main Authors: Francischetti, Ivo M.B., Saliou, Bernard, Leduc, Mireille, R. Carlini, Celia, Hatmi, Mohamed, Randon, Jacques, Faili, Ahmad, Bon, Cassian
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animal poisons toxicology. Antivenoms; Animals; Binding, Competitive; Biological and medical sciences; Blood Platelets - metabolism; Crotalid Venoms - blood; Crotalid Venoms - chemistry; Crotalus durissus terrificus; Hemagglutination Tests; Iodine Radioisotopes; Lectins, C-Type; Male; Medical sciences; Molecular Sequence Data; Molecular Structure; Platelet Aggregation - drug effects; Protein Binding; Rabbits; Radioligand Assay; Sequence Homology, Amino Acid; Toxicology
• ISSN: 0041-0101; 1879-3150
• DOI: 10.1016/S0041-0101(97)00021-4

Convulxin, a very potent aggregating protein from rattlesnake venom, was purified by a new procedure and its heterodimeric structure α 3 μ 3 was confirmed. The polypeptide N-terminal sequences of convulxin subunits were determined by Edman degradation. They are very similar and appear homologous to botrocetin from Bothrops jararaca venom and to rattlesnake lectin from Crotalus atrox venom, both being classified among the C-type lectin family. The binding of 125I-labelled convulxin to blood platelets has also been analysed under equilibrium conditions. These studies indicated that convulxin binds to platelets with a high affinity ( d = 30 pM) on a small number of binding sites (1000 binding sites per cell). The high-affinity binding of convulxin appears specific to platelets, since it is not observed on other cell types such as neutrophils and erythrocytes. Also, the high-affinity binding of convulxin to membranes platelet is not inhibited by α-thrombin, fibrinogen, collagen, laminin binding inhibitor, RGDS peptide, adenosine diphosphate, platelet-activating factor-acether, serotonin or epinephrine. This, together with the recent observation that platelet activation by convulxin is partially mediated by phospholipase C and involves other mechanisms as well, indicates that convulxin may interact with a specific platelet acceptor (receptor) protein which has yet to be characterized.