Kowalska M A, Tan L, Holt J C, Peng M, Karczewski J, Calvete J J, Niewiarowski S
Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Thromb Haemost. 1998 Mar;79(3):609-13.
Viper venoms contain a variety of platelet binding proteins including those which bind to platelet GPIb/GPIX. Most of these proteins inhibit von Willebrand factor mediated platelet agglutination. Here we report the primary structures of unique members of this family, alboaggregins A and B, isolated from Trimeresurus albolabris, which have the ability to stimulate platelet agglutination and aggregation. Four chains of alboaggregin A and two chains of alboaggregin B share a high degree of homology and all cysteines in both alboaggregins are conserved. Both alboaggregins caused similar agglutination of fixed platelets. Alboaggregin A induced platelet aggregation and release reaction with EC50 = 10 and 30 nM, respectively, which is 20-fold lower than those for alboaggregin B. These observations suggest that the dimeric structure of alboaggregin B is sufficient to mediate its binding to GPIb and induce agglutination of platelets whereas aggregation and release reaction are significantly enhanced by tetrameric structure of alboaggregin A.
蝰蛇毒液含有多种血小板结合蛋白，包括那些与血小板糖蛋白Ib/IX结合的蛋白。这些蛋白大多抑制血管性血友病因子介导的血小板凝集。在此，我们报告从白唇竹叶青中分离出的该家族独特成员——白聚凝血素A和B的一级结构，它们具有刺激血小板凝集和聚集的能力。白聚凝血素A的四条链和白聚凝血素B的两条链具有高度同源性，且两种白聚凝血素中的所有半胱氨酸均保守。两种白聚凝血素均引起固定血小板的相似凝集。白聚凝血素A诱导血小板聚集和释放反应，其半数有效浓度（EC50）分别为10 nM和30 nM，比白聚凝血素B低20倍。这些观察结果表明，白聚凝血素B的二聚体结构足以介导其与糖蛋白Ib的结合并诱导血小板凝集，而白聚凝血素A的四聚体结构则显著增强聚集和释放反应。
