The large conformational changes of Hsp90 are only weakly coupled to ATP hydrolysis
The large conformational changes of Hsp90 are only weakly coupled to ATP hydrolysis
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DOI：
10.1038/nsmb.1557
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发表时间：
2009-03-01
影响因子：
16.8
通讯作者：
Hugel, Thorsten
中科院分区：
文献类型：
--
作者：
Mickler, Moritz;Hessling, Martin;Hugel, Thorsten
分子伴侣热休克蛋白90 （Hsp90）是真核细胞中最丰富的蛋白之一。它的功能依赖于异常缓慢的atp酶反应，该反应涉及大的构象变化。为了观察这些构象变化并了解它们与atp酶功能的相互作用，我们开发了一种单分子检测方法，可以在各种核苷酸条件下实时检测酵母Hsp90二聚体。我们在时间尺度上检测到开放和封闭状态之间的构象波动比ATP水解速率快得多。编译的停留时间分布使我们能够将所有速率常数分配到Hsp90构象变化的最小动力学模型中，并描绘ATP水解的影响。出乎意料的是，在这个模型中，ATP几乎对称地降低了两个能垒，以至于几乎没有引入方向性。相反，Hsp90的随机热波动是主导过程。(c) 2009 Nature America, Inc。版权所有。
The molecular chaperone heat-shock protein 90 (Hsp90) is one of the most abundant proteins in unstressed eukaryotic cells. Its function is dependent on an exceptionally slow ATPase reaction that involves large conformational changes. To observe these conformational changes and to understand their interplay with the ATPase function, we developed a single-molecule assay that allows examination of yeast Hsp90 dimers in real time under various nucleotide conditions. We detected conformational fluctuations between open and closed states on timescales much faster than the rate of ATP hydrolysis. The compiled distributions of dwell times allow us to assign all rate constants to a minimal kinetic model for the conformational changes of Hsp90 and to delineate the influence of ATP hydrolysis. Unexpectedly, in this model ATP lowers two energy barriers almost symmetrically, such that little directionality is introduced. Instead, stochastic, thermal fluctuations of Hsp90 are the dominating processes. (c) 2009 Nature America, Inc. All rights reserved.