Structural Basis for Actin Assembly, Activation of ATP Hydrolysis, and Delayed Phosphate Release
Structural Basis for Actin Assembly, Activation of ATP Hydrolysis, and Delayed Phosphate Release
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DOI：
10.1016/j.cell.2010.09.034
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发表时间：
2010-10-15
期刊：
影响因子：
64.5
通讯作者：
Wakabayashi, Takeyuki
中科院分区：
文献类型：
--
作者：
Murakami, Kenji;Yasunaga, Takuo;Wakabayashi, Takeyuki
组装的肌动蛋白丝支持细胞信号传导、细胞内运输和胞质分裂。肌动蛋白组装引发的 ATP 水解为体内丝的周转提供了结构线索。在这里，我们展示了磷酸盐存在下丝状肌动蛋白（F-肌动蛋白）的冷冻电子显微镜（cryo-EM）结构，以及一些α螺旋主链和大侧链的可视化。基于 EM 图的完整原子模型确定了由结合的镁离子和磷酸盐离子介导的分子间相互作用。 F-肌动蛋白模型与 G-肌动蛋白单体晶体结构的比较揭示了保守的富含脯氨酸环的弯曲在 ATP 水解后触发磷酸盐释放中的关键作用。 G-肌动蛋白的晶体结构表明，该环中的突变将催化位点捕获在 ATP 酶循环的两个中间状态。组合的结构信息使我们能够提出生化事件的详细分子机制，包括肌动蛋白聚合和 ATP 酶激活，这对肌动蛋白丝动力学至关重要。
Assembled actin filaments support cellular signaling, intracellular trafficking, and cytokinesis. ATP hydrolysis triggered by actin assembly provides the structural cues for filament turnover in vivo. Here, we present the cryo-electron microscopic (cryo-EM) structure of filamentous actin (F-actin) in the presence of phosphate, with the visualization of some alpha-helical backbones and large side chains. A complete atomic model based on the EM map identified intermolecular interactions mediated by bound magnesium and phosphate ions. Comparison of the F-actin model with G-actin monomer crystal structures reveals a critical role for bending of the conserved proline-rich loop in triggering phosphate release following ATP hydrolysis. Crystal structures of G-actin show that mutations in this loop trap the catalytic site in two intermediate states of the ATPase cycle. The combined structural information allows us to propose a detailed molecular mechanism for the biochemical events, including actin polymerization and ATPase activation, critical for actin filament dynamics.