Department of Biochemistry , University of Alberta , Edmonton , Alberta T6G 2H7 , Canada.
Department of Cell Biology , University of Alberta , Edmonton , Alberta T6G 2H7 , Canada.
Biochemistry. 2019 Apr 9;58(14):1869-1877. doi: 10.1021/acs.biochem.9b00144. Epub 2019 Mar 22.
Hsp90 is a crucial chaperone whose ATPase activity is fundamental for stabilizing and activating a diverse array of client proteins. Binding and hydrolysis of ATP by dimeric Hsp90 drive a conformational cycle characterized by fluctuations between a compact, N- and C-terminally dimerized catalytically competent closed state and a less compact open state that is largely C-terminally dimerized. We used F and H dynamic nuclear magnetic resonance (NMR) spectroscopy to study the opening and closing kinetics of Hsp90 and to determine the k for ATP hydrolysis. We derived a set of coupled ordinary differential equations describing the rate laws for the Hsp90 kinetic cycle and used these to analyze the NMR data. We found that the kinetics of closing and opening for the chaperone are slow and that the lower limit for k of ATP hydrolysis is ∼1 s. Our results show that the chemical step is optimized and that Hsp90 is indeed a "perfect" enzyme.
热休克蛋白 90（Hsp90）是一种关键的伴侣蛋白，其 ATP 酶活性对于稳定和激活各种客户蛋白至关重要。二聚体 Hsp90 与 ATP 的结合和水解驱动构象循环，其特征是在紧密的、N 端和 C 端二聚化的催化活性封闭状态和非紧密的开放状态之间波动，开放状态主要是 C 端二聚化。我们使用 F 和 H 动态核磁共振（NMR）光谱研究 Hsp90 的打开和关闭动力学，并确定 ATP 水解的 k。我们推导出了一组描述 Hsp90 动力学循环的速率定律的耦合常微分方程，并使用这些方程来分析 NMR 数据。我们发现，伴侣蛋白的关闭和打开动力学较慢，ATP 水解的 k 的下限约为 1 s。我们的结果表明，化学步骤得到了优化，Hsp90 确实是一种“完美”的酶。
