Department of Chemistry, University of Science and Technology of China, No. 96, Jinzhai Road, Hefei 230026, PR China.
Toxicon. 2010 Jun 15;55(7):1358-64. doi: 10.1016/j.toxicon.2010.02.010. Epub 2010 Feb 13.
Factor IX-binding protein (AHP IX-bp), a Ca2+- and Zn2+-binding protein from the venom of Agkistrodon Halys Pallas was reported to bind specifically with factor IX in a Zn2+-dependent manner. Here we have purified AHP IX-bp by a simple two-step of chromatography procedure and found that AHP IX-bp also binds factor Xa (FXa) with high binding-affinity in a Mg2+-dependent manner. Although Mg2+ ions have a significantly low binding-affinity for apo-AHP IX-bp as determined by isothermal titration calorimetry, they can induce the binding of apo-AHP IX-bp with FXa even in the absence of Ca2+ as determined by native PAGE and surface plasmon resonance. Mg2+ ions are required to maintain in vivo function of FX Gla domain for its recognition of AHP IX-bp. Both Ca2+ and Zn2+ ions fail to induce the binding between apo-AHP IX-bp and FXa. The abundant Mg2+ ions in blood play an important role in the anticoagulation of AHP IX-bp.
因子 IX 结合蛋白（AHP IX-bp）是来自尖吻蝮蛇毒液的一种 Ca2+和 Zn2+结合蛋白，据报道它以 Zn2+依赖的方式特异性结合因子 IX。在这里，我们通过简单的两步层析程序对 AHP IX-bp 进行了纯化，并发现 AHP IX-bp 还以 Mg2+依赖的方式与因子 Xa（FXa）具有高结合亲和力。尽管通过等温热力学滴定法测定，apo-AHP IX-bp 与 Mg2+离子的结合亲和力明显较低，但通过 native PAGE 和表面等离子体共振测定，它们可以诱导 apo-AHP IX-bp 与 FXa 的结合，即使在没有 Ca2+的情况下也是如此。Mg2+离子对于 FX Gla 结构域识别 AHP IX-bp 的体内功能是必需的。Ca2+和 Zn2+离子都不能诱导 apo-AHP IX-bp 与 FXa 之间的结合。血液中丰富的 Mg2+离子在 AHP IX-bp 的抗凝作用中发挥重要作用。
