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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of coagulation factor IX-binding protein from habu snake venom at 2.6 A: implication of central loop swapping based on deletion in the linker region.
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Crystal structure of coagulation factor IX-binding protein from habu snake venom at 2.6 A: implication of central loop swapping based on deletion in the linker region.

机译：来自哈布蛇毒的凝血因子IX结合蛋白在2.6 A时的晶体结构：基于在接头区域的缺失而引起的中央环交换。

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Coagulation factor IX-binding protein (IX-bp) isolated from the venom of the habu snake (Trimeresurus flavoviridis) is a disulfide-linked heterodimer consisting of homologous subunits A and B. The structure of IX-bp has been solved by X-ray crystallography at 2.6 A resolution to a crystallographic R -value of 0.181. The main-chain fold of each subunit is homologous to the carbohydrate-recognition domain of C-type lectins (C-type CRDs) except for the extended central loop. The structure is almost identical with that of factors IX and X-binding protein (IX/X-bp) as expected from the high level of amino acid sequence homology. The functional difference in ligand recognition from IX/X-bp must reside in the amino acid differences. A continuity of different amino acid residues located from the C-terminal of the second alpha-helix to the following loop forms the local conformational difference in this region between the two proteins. This loop participates in the formation of the concave surface between the two subunits, the putative binding site for the Gla-domain (gamma-carboxyglutamic acid-containing domain) of the coagulation factors. Another difference between the two proteins is in the relative disposition of subunits A and B. When the B subunits are superimposed, about a 6 degrees rotation is required for the superposition of the A subunits. A calcium ion links the second alpha-helix region to the C-terminal tail in each subunit and helps to stabilize the structure for Gla-domain binding. The interface created by the central loop swapping in the dimer IX-bp is almost identical with that seen within the monomeric C-type CRDs. This dimer forms as the result of the amino acid deletion in the linker region of the central loop of the original C-type lectins. Such a dimerization disrupts the lectin active site and creates a Gla-domain binding site, imparting functional diversity. Copyright 1999 Academic Press.
机译：从蛇蛇毒（Trimeresurus flavoviridis）毒液中分离得到的凝血因子IX结合蛋白（IX-bp）是由二硫键连接的异二聚体，由同源的亚基A和B组成。X-射线已解决了IX-bp的结构问题2.6 A分辨率的晶体学，R值为0.181。除扩展的中央环外，每个亚基的主链折叠与C型凝集素（C型CRD）的碳水化合物识别结构域同源。从高水平的氨基酸序列同源性预期，该结构与因子IX和X结合蛋白（IX / X-bp）的结构几乎相同。与IX / X-bp进行配体识别的功能差异必​​须存在于氨基酸差异中。从第二个α-螺旋的C末端到随后的环的不同氨基酸残基的连续性在两种蛋白之间的该区域中形成局部构象差异。该环参与两个亚基之间的凹面的形成，这是凝血因子的Gla结构域（含γ-羧基谷氨酸的结构域）的假定结合位点。两种蛋白质之间的另一个区别在于亚基A和B的相对位置。当B亚基重叠时，A亚基的重叠大约需要旋转6度。钙离子将第二个α-螺旋区域连接到每个亚基的C末端尾部，并有助于稳定Gla结构域结合的结构。在二聚体IX-bp中由中心环交换产生的接口与在单体C型CRD中看到的接口几乎相同。该二聚体是原始C型凝集素中央环连接区氨基酸缺失的结果。这种二聚化破坏了凝集素活性位点并产生了Gla结构域结合位点，从而赋予了功能多样性。版权所有1999，学术出版社。

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