Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany.
Bavarian NMR Center and Center for Integrated Protein Science Munich, Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85747, Garching, Germany.
Chembiochem. 2021 Mar 16;22(6):1084-1092. doi: 10.1002/cbic.202000699. Epub 2020 Dec 9.
The molecular chaperone Hsp90 supports the functional activity of specific substrate proteins (clients). For client processing, the Hsp90 dimer undergoes a series of ATP-driven conformational rearrangements. Flexible linkers connecting the three domains of Hsp90 are crucial to enable dynamic arrangements. The long charged linker connecting the N-terminal (NTD) and middle (MD) domains exhibits additional functions in vitro and in vivo. The structural basis for these functions remains unclear. Here, we characterize the conformation and dynamics of the linker and NTD-MD domain interactions by NMR spectroscopy. Our results reveal two regions in the linker that are dynamic and exhibit secondary structure conformation. We show that these regions mediate transient interactions with strand β8 of the NTD. As a consequence, this strand detaches and exposes a hydrophobic surface patch, which enables binding to the p53 client. We propose that the charged linker plays an important regulatory role by coupling the Hsp90 NTD-MD arrangement with the accessibility of a client binding site on the NTD.
分子伴侣 Hsp90 支持特定底物蛋白（客户）的功能活性。对于客户处理，Hsp90 二聚体经历一系列 ATP 驱动的构象重排。连接 Hsp90 的三个结构域的柔性接头对于实现动态排列至关重要。连接 N 端（NTD）和中间（MD）结构域的长电荷接头在体外和体内具有额外的功能。这些功能的结构基础仍不清楚。在这里，我们通过 NMR 光谱表征了接头和 NTD-MD 结构域相互作用的构象和动力学。我们的结果揭示了接头中两个动态的区域，并且具有二级结构构象。我们表明，这些区域与 NTD 的β8 链间进行瞬时相互作用。因此，这条链脱离并暴露出一个疏水面，从而能够与 p53 客户结合。我们提出，带电荷的接头通过将 Hsp90 NTD-MD 排列与 NTD 上客户结合位点的可及性相偶联，发挥重要的调节作用。
