Institute of Physical Chemistry, University of Freiburg, Freiburg im Breisgau, Germany; Signalling Research Centers BIOSS and CIBSS, University of Freiburg, Freiburg im Breisgau, Germany.
Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
Biophys J. 2023 Sep 5;122(17):3458-3468. doi: 10.1016/j.bpj.2023.07.020. Epub 2023 Jul 27.
The heat shock protein 90 (Hsp90) is a molecular chaperone, which plays a key role in eukaryotic protein homeostasis. Co-chaperones assist Hsp90 in client maturation and in regulating essential cellular processes such as cell survival, signal transduction, gene regulation, hormone signaling, and neurodegeneration. Aha1 (activator of Hsp90 ATPase) is a unique co-chaperone known to stimulate the ATP hydrolysis of Hsp90, but the mechanism of their interaction is still unclear. In this report, we show that one or two Aha1 molecules can bind to one Hsp90 dimer and that the binding stoichiometry affects Hsp90's conformation, kinetics, ATPase activity, and stability. In particular, a coordination of two Aha1 molecules can be seen in stimulating the ATPase activity of Hsp90 and the unfolding of the middle domain, whereas the conformational equilibrium and kinetics are hardly affected by the stoichiometry of bound Aha1. Altogether, we show a regulation mechanism through the stoichiometry of Aha1 going far beyond a regulation of Hsp90's conformation.
热休克蛋白 90（Hsp90）是一种分子伴侣，在真核生物蛋白质稳态中起着关键作用。共伴侣协助 Hsp90 完成客户成熟，并调节重要的细胞过程，如细胞存活、信号转导、基因调控、激素信号和神经退行性变。Aha1（Hsp90 ATP 酶激活剂）是一种独特的共伴侣，已知其能刺激 Hsp90 的 ATP 水解，但它们相互作用的机制仍不清楚。在本报告中，我们表明，一个或两个 Aha1 分子可以结合到一个 Hsp90 二聚体上，并且结合的化学计量会影响 Hsp90 的构象、动力学、ATP 酶活性和稳定性。特别是，我们可以看到两个 Aha1 分子的协调作用可以刺激 Hsp90 的 ATP 酶活性和中间结构域的展开，而构象平衡和动力学几乎不受结合的 Aha1 化学计量的影响。总之，我们展示了一种通过 Aha1 化学计量进行调节的机制，远远超出了对 Hsp90 构象的调节。
