Takeya H, Nishida S, Miyata T, Kawada S, Saisaka Y, Morita T, Iwanaga S
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
J Biol Chem. 1992 Jul 15;267(20):14109-17.
We determined the complete amino acid sequence of RVV-X, the blood coagulation factor X activating enzyme, isolated from Russell's viper venom and studied structure-function relationships. RVV-X (M(r) 79,000) consists of a disulfide-bonded two-chain glycoprotein with a heavy chain of M(r) 59,000 and a light chain of heterogeneous M(r) 18,000 (LC1) and 21,000 (LC2). These chains were separated after reduction and S-pyridylethylation, and the isolated major component LC1 was used for sequence analysis. The heavy chain consists of 427 residues containing four asparagine-linked oligosaccharides, and its entire sequence was similar to that of the high molecular mass hemorrhagic protein, HR1B, isolated from the venom of Trimere-surus flavoviridis. The heavy chain contains three distinct domains, metalloproteinase, disintegrin (platelet aggregation inhibitor)-like and unknown cysteine-rich domains. On the other hand, light chain LC1 consists of 123 amino acid residues containing one asparagine-linked oligosaccharide and shows sequence homology similar to that found in the so-called C-type (Ca(2+)-dependent) lectins. Therefore, RVV-X is a novel metalloproteinase containing a mosaic structure with distintegrin-like, cysteine-rich, and C-type lectin-like domains. RVV-X potently inhibits collagen- and ADP-stimulated platelet aggregations, probably via its distintegrin-like domain, although this domain does not contain the Arg-Gly-Asp sequence which is conserved in various venom distintegrins and which is thought to be one of the interaction sites for platelet integrins. Our findings also indicate that snake venom factor IX/factor X-binding protein with a C-type lectin structure (Atoda, H., Hyuga, M., and Morita, T. (1991) J. Biol. Chem. 266, 14903-14911) inhibits RVV-X-catalyzed factor X activation; hence, the light chain of RVV-X probably participates in recognizing some portion of the zymogen factor X.
我们测定了从锯鳞蝰蛇毒中分离得到的血液凝固因子X激活酶——RVV-X的完整氨基酸序列，并研究了其结构与功能的关系。RVV-X（相对分子质量79,000）是一种由二硫键连接的双链糖蛋白，重链相对分子质量为59,000，轻链相对分子质量不均一，分别为18,000（LC1）和21,000（LC2）。还原和S-吡啶乙基化后，这些链被分开，分离得到的主要成分LC1用于序列分析。重链由427个残基组成，含有4个天冬酰胺连接的寡糖，其整个序列与从竹叶青蛇毒中分离得到的高分子量出血蛋白HR1B相似。重链包含三个不同的结构域，金属蛋白酶结构域、解整合素（血小板聚集抑制剂）样结构域和未知的富含半胱氨酸结构域。另一方面，轻链LC1由123个氨基酸残基组成，含有1个天冬酰胺连接的寡糖，其序列同源性与在所谓的C型（钙依赖性）凝集素中发现的相似。因此，RVV-X是一种新型金属蛋白酶，具有解整合素样、富含半胱氨酸和C型凝集素样结构域的镶嵌结构。RVV-X能有效抑制胶原和ADP刺激的血小板聚集，可能是通过其解整合素样结构域，尽管该结构域不包含在各种蛇毒解整合素中保守的精氨酸-甘氨酸-天冬氨酸序列，而该序列被认为是血小板整合素的相互作用位点之一。我们的研究结果还表明，具有C型凝集素结构的蛇毒因子IX/因子X结合蛋白（阿托达，H.，日向，M.，和森田，T.（1991）《生物化学杂志》266，14903 - 14911）能抑制RVV-X催化的因子X激活；因此，RVV-X的轻链可能参与识别酶原因子X的某些部分。
