Takeya H, Oda K, Miyata T, Omori-Satoh T, Iwanaga S
Department of Molecular Biology, Graduate School of Medical Science, Faculty of Science, Kyushu University, Fukuoka, Japan.
J Biol Chem. 1990 Sep 25;265(27):16068-73.
Hemorrhage is a common occurrence in a victim bitten by crotalid and viperid snakes, and hemorrhagic components in these various venoms have been isolated and characterized. Previously, we have shown that a low molecular weight hemorrhagic protein (HR2a, 202 amino acid residues) isolated from the venom of Trimeresurus flavoviridis is a member of a new subfamily of metalloproteinases. We now report the complete amino acid sequence of a high molecular mass hemorrhagic protein isolated from the same venom. This protein, HR1B, is a mosaic protein composed of 416 residues containing four asparagine-linked oligosaccharide chains. The amino-terminal half (residues 1-203) of HR1B contains a metalloproteinase domain, the sequence of which is 62% identical to that of HR2a and 52% identical to that of hemorrhagic toxin d isolated from Crotalus atrox venom. The most interesting finding is that the middle region (residues 204-300) of HR1B shows a striking similarity to disintegrins, Arg-Gly-Asp-containing platelet aggregation inhibitors, recently found in several viper venoms. Interestingly, however, this region of HR1B does not contain the Arg-Gly-Asp sequence which is known to be a putative binding site in the disintegrins for the platelet fibrinogen receptor, the glycoprotein IIb-IIIa complex. We also found that the carboxyl-terminal region (residues 213-336) of the middle part of HR1B shows 30% identity to residues 1543-1656 of von Willebrand factor and that the remaining region at the carboxyl-terminal end is unique and has a cysteine-rich sequence. These results suggest that the middle portion of HR1B, which shows structural similarities to the disintegrins and von Willebrand factor, may be important in synergistically stimulating hemorrhagic activity in the NH2-terminal metalloproteinase domain.
出血是被蝰蛇科和蝮蛇科蛇咬伤的受害者的常见症状，并且已经从这些不同毒液中分离并鉴定出了出血成分。此前，我们已经表明，从竹叶青蛇毒液中分离出的一种低分子量出血蛋白（HR2a，202个氨基酸残基）是金属蛋白酶新亚家族的成员。我们现在报告从同一毒液中分离出的一种高分子量出血蛋白的完整氨基酸序列。这种蛋白，HR1B，是一种由416个残基组成的镶嵌蛋白，含有四条天冬酰胺连接的寡糖链。HR1B的氨基末端一半（残基1 - 203）包含一个金属蛋白酶结构域，其序列与HR2a的序列有62%的同一性，与从西部菱斑响尾蛇毒液中分离出的出血毒素d的序列有52%的同一性。最有趣的发现是，HR1B的中间区域（残基204 - 300）与去整合素（含精氨酸 - 甘氨酸 - 天冬氨酸的血小板聚集抑制剂）有显著相似性，去整合素最近在几种蝰蛇毒液中被发现。然而，有趣的是，HR1B的这个区域不包含精氨酸 - 甘氨酸 - 天冬氨酸序列，而该序列是已知的去整合素中与血小板纤维蛋白原受体（糖蛋白IIb - IIIa复合物）的假定结合位点。我们还发现，HR1B中间部分的羧基末端区域（残基213 - 336）与血管性血友病因子的残基1543 - 1656有30%的同一性，并且羧基末端的其余区域是独特的，有一个富含半胱氨酸的序列。这些结果表明，HR1B的中间部分与去整合素和血管性血友病因子在结构上相似，可能在协同刺激氨基末端金属蛋白酶结构域的出血活性方面很重要。
