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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >High resolution crystal structures of free thrombin in the presence of K+ reveal the molecular basis of monovalent cation selectivity and an inactive slow form
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High resolution crystal structures of free thrombin in the presence of K+ reveal the molecular basis of monovalent cation selectivity and an inactive slow form

机译：K +存在下游离凝血酶的高分辨率晶体结构揭示了单价阳离子选择性和非活性慢形式的分子基础

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摘要

Structural biology has recently advanced our understanding of the molecular mechanisms of activation and selectivity in monovalent cation activated enzymes. Here we report a 1.9 angstrom resolution crystal structure of free thrombin, a Na+ selective enzyme, in the presence of KCl There are two molecules in the asymmetric unit, one with the cation site bound to K+ and the other with this site free. The K-bound form shows key differences compared with the Na+-bound structure that explain the different kinetics of activation. The cation-free form, on the other hand, assumes a conformation where the monovalent cation binding site is completely disordered, the S1 pocket is inaccessible to substrate and binding to exosite I is compromised by an unprecedented > 20 angstrom shift in the position of the alltolysis loop. This form, named S*, corresponds to the inactive Na+-free slow form identified by early kinetic studies. A simple model of thrombin allostery that incorporates the contribution of S* is proposed. (c) 2005 Elsevier B.V. All rights reserved.
机译：最近，结构生物学提高了我们对单价阳离子活化酶中活化和选择性分子机制的理解。在这里，我们报告了在存在KCl的情况下，游离凝血酶（一种Na +选择性酶）的1.9埃分辨率晶体结构，在不对称单元中有两个分子，一个分子的阳离子位点与K +结合，另一个分子带该位点的游离。与Na +结合的结构相比，K结合的形式显示出关键的差异，这说明了活化的不同动力学。另一方面，不含阳离子的形式则具有这样的构型：单价阳离子结合位点完全无序，底物无法进入S1口袋，与异位点I的结合受到前所未有的> 20埃位移的损害。溶酶循环。这种形式称为S *，与早期动力学研究确定的无活性的无Na +慢形式相对应。提出了一个简单的凝血酶变构模型，该模型结合了S *的贡献。 （c）2005 Elsevier B.V.保留所有权利。

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