Fujimura Y, Ikeda Y, Miura S, Yoshida E, Shima H, Nishida S, Suzuki M, Titani K, Taniuchi Y, Kawasaki T
Department of Blood Transfusion, Nara Medical University, Japan.
Thromb Haemost. 1995 Aug;74(2):743-50.
A platelet glycoprotein Ib-binding protein (GPIb-BP) was isolated from the snake venom of Bothrops jararaca. Jararaca GPIb-BP showed a single band with M(r) of 30,000, and two distinct bands with M(r) of 17,000/13,000 under non-reducing and reducing conditions, respectively, on SDS-polyacrylamide gel electrophoresis. Jararaca GPIb-BP itself induced neither platelet aggregation nor serotonin release from platelets, but specifically bound to GPIb (40,629 +/- 2,521 molecules per normal platelet, with Kd 39.1 +/- 2.4 nM at saturation). The purified venom protein completely inhibited ristocetin- or botrocetin-induced von Willebrand factor (vWF) binding, and blocked the bovine vWF binding to GPIb, with IC50 values ranging from 28 to 42 nM, without affecting the platelet aggregation induced by ADP or alpha-thrombin. 125I-jararaca GPIb-BP binding to GPIb was not altered by the presence of human alpha-thrombin. Jararaca GPIb-BP at a final concentration of 104 nM totally abolished vWF-dependent shear-induced platelet aggregation (SIPA) at a high shear stress, but had no effect on SIPA at a low shear stress. Reduced and S-carboxyamido-methylated jararaca GPIb-BP lost its inhibitory activity on SIPA. The NH2-terminal amino acid sequences of the subunits revealed a high degree of homology with those of several Ca(2+)-dependent lectins, especially to those of two functionally opposite venom proteins, botrocetin (a vWF-modulator) and alboaggregin-B (a GPIb-modulator).
从巴西矛头蝮蛇毒中分离出一种血小板糖蛋白 Ib 结合蛋白（GPIb - BP）。在 SDS - 聚丙烯酰胺凝胶电泳中，巴西矛头蝮蛇 GPIb - BP 在非还原条件下呈现一条分子量为 30,000 的条带，在还原条件下分别呈现两条分子量为 17,000/13,000 的不同条带。巴西矛头蝮蛇 GPIb - BP 本身既不诱导血小板聚集，也不引起血小板释放 5 - 羟色胺，但能特异性结合 GPIb（每个正常血小板有 40,629 ± 2,521 个分子，饱和时 Kd 为 39.1 ± 2.4 nM）。纯化的毒液蛋白完全抑制瑞斯托霉素或博曲酶诱导的血管性血友病因子（vWF）结合，并阻断牛 vWF 与 GPIb 的结合，IC50 值在 28 至 42 nM 之间，且不影响 ADP 或α - 凝血酶诱导的血小板聚集。人α - 凝血酶的存在不改变 125I - 巴西矛头蝮蛇 GPIb - BP 与 GPIb 的结合。终浓度为 104 nM 的巴西矛头蝮蛇 GPIb - BP 在高剪切应力下完全消除 vWF 依赖的剪切诱导血小板聚集（SIPA），但在低剪切应力下对 SIPA 无影响。还原和 S - 羧酰胺甲基化的巴西矛头蝮蛇 GPIb - BP 失去对 SIPA 的抑制活性。亚基的 NH2 - 末端氨基酸序列与几种 Ca(2 +) 依赖性凝集素的序列高度同源，尤其是与两种功能相反的毒液蛋白博曲酶（一种 vWF 调节剂）和 alboaggregin - B（一种 GPIb 调节剂）的序列高度同源。
