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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Atomic resolution structure of squash trypsin inhibitor: unexpected metal coordination.
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Atomic resolution structure of squash trypsin inhibitor: unexpected metal coordination.

机译：原子分辨率南瓜胰蛋白酶的结构抑制剂:意想不到的金属协调。

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摘要

CMTI-I, a small-protein trypsin inhibitor, has been crystallized as a 4:1 protein-zinc complex. The metal is coordinated in a symmetric tetrahedral fashion by glutamate/glutamic acid side chains. The structure was solved by direct methods in the absence of prior knowledge of the special position metal centre and refined with anisotropic displacement parameters using diffraction data extending to 1.03 A. In the final calculations, the main-chain atoms of low B(eq) values were refined without restraint control. The two molecules in the asymmetric unit have a conformation that is very similar to that reported earlier for CMTI-I in complex with trypsin, despite the Met8Leu mutation of the present variant. The only significant differences are in the enzyme-binding epitope (including the Arg5 residue) and in a higher mobility loop around Glu24. The present crystal structure contains organic solvent molecules (glycerol, MPD) that interact with the inhibitor molecules in an area that is at the enzyme-inhibitorinterface in the CMTI-I-trypsin complex. A perfectly ordered residue (Ala18) has an unusual Ramachandran conformation as a result of geometrical strain introduced by the three disulfide bridges that clamp the protein fold. The results confirm deficiencies of some stereochemical restraints, such as peptide planarity or the N-C(alpha)-C angle, and suggest a link between their violations and hydrogen bonding.
机译：CMTI-I,小型蛋白质胰蛋白酶抑制剂,结晶是4:1 protein-zinc复杂。金属是协调对称的四面体时尚谷氨酸/谷氨酸侧链。在缺乏先验知识的方法金属中心和精制的特殊位置各向异性位移参数使用衍射数据扩展到1.03。最后计算,主链原子的低B (eq)价值观提炼不克制控制。有一个构象很相似吗早些时候报道的CMTI-I复杂胰蛋白酶,尽管Met8Leu变异的现在的变体。在enzyme-binding抗原决定基(包括Arg5残渣)和高流动循环Glu24左右。包含有机溶剂分子(甘油、MPD)与抑制剂分子交互是在一个区域在CMTI-I-trypsin enzyme-inhibitorinterface复杂。一个不寻常的拉马钱德兰构象引入的几何变形的三个二硫桥夹蛋白质折叠。结果确认的缺陷立体化学的限制,如肽平面性或c - c角(α),和建议他们的侵犯和氢之间的联系成键。

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