Coagulation factor X-binding protein from Deinagkistrodon acutus venom is a Gla domain-binding protein
Coagulation factor X-binding protein from Deinagkistrodon acutus venom is a Gla domain-binding protein
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DOI：
10.1021/bi981177x
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发表时间：
1998-12-15
期刊：
影响因子：
2.9
通讯作者：
Morita, T
中科院分区：
文献类型：
--
作者：
Atoda, H;Ishikawa, M;Morita, T
因子IX/因子x结合蛋白（IX/X-bp）是从黄毒蛇毒中分离出来的一种抗凝血剂，主要与因子IX结合。本研究从百步蛇Deinagkistrodon acutus（百步蛇）毒液中分离出与IX/X-bp结合特性不同的IX/X-bp样蛋白。研究了主要抗凝蛋白X-bp的全氨基酸序列和结合特性。X-bp与固相因子X和IX的半最大结合浓度分别为0.4和3 nM。X-bp与固相因子X的结合分别被6倍和9倍过量浓度的因子X和Gla结构域（GD）肽1-44抑制50%，但不受GD肽1-41和Gla结构域因子X的影响。X-bp每分子结合2个Ca2+离子，K-d值为16 +/- 0.7（平均+/- SE， n = 6）和103 +/- 10 μ M. X-bp是c型凝集素样亚基的异源二聚体。16 kDa链（A链）由129个氨基酸残基组成，与IX/X-bp的A链序列相同68%。15 kDa链（B链）由123个氨基酸残基组成，与IX/X-bp有87%的同源性，利用已知IX/X-bp的折叠面构建三维模型，发现与IX/X-bp不同的氨基酸残基多位于分子表面。其中一些集中在凹表面的一部分，被认为是凝血因子结合位点，可能是配体结合的鉴别器。这些结果表明，从蝮蛇毒液中分离到的X-bp是一种GD结合蛋白，GD肽的c端区域是GD肽折叠的关键区域。
Factor IX/factor X-binding protein (IX/X-bp) is an anticoagulant isolated from the venom of Trimeresurus flavoviridis (habu snake) and binds predominantly to factor IX. In this study, we isolated IX/X-bp-like proteins from the venom of Deinagkistrodon acutus (hundred pace snake) with binding characteristics different from those of IX/X-bp. The complete amino acid sequence and binding characteristics of the main anticoagulant protein, named X-bp, were investigated. The concentrations of X-bp at half-maximal binding to solid-phase factors X and IX were 0.4 and 3 nM, respectively. The binding of X-bp to solid-phase factor X was inhibited by 50% by 6- and 9-fold excess concentrations of factor X and Gla domain (GD) peptide 1-44, respectively, but was not influenced by GD peptide 1-41 and Gla domainless factor X. X-bp bound two Ca2+ ions per molecule with K-d values of 16 +/- 0.7 (mean +/- SE, n = 6) and 103 +/- 10 mu M. X-bp was a heterodimer of C-type lectin-like subunits. The 16 kDa chain (A chain) consisted of 129 amino acid residues and was 68% identical to the sequence of the A chain of IX/X-bp. The 15 kDa chain (B chain) consisted of 123 amino acid residues and was 87% identical to IX/X-bp, Three-dimensional model construction from the known fold of IX/X-bp showed that amino acid residues different from those of IX/X-bp are mostly on the molecular surface. Some of these are concentrated on a part of the concave surface which is considered to be the coagulation factor-binding site, presumably acting as a discriminator for ligand binding. These results indicated that X-bp isolated from D. acutus venom was a GD-binding protein, and the C-terminal region of GD peptide was critical for folding of the peptide.