Centro Nacional de Biotecnología (CNB-CSIC), Darwin, 3, 28049 Madrid, Spain.
Center for Integrated Protein Science (CIPSM) at the Department Chemie, Technische Universität München, 85747 Garching, Germany.
Nat Commun. 2014 Nov 19;5:5484. doi: 10.1038/ncomms6484.
In eukarya, chaperones Hsp70 and Hsp90 act coordinately in the folding and maturation of a range of key proteins with the help of several co-chaperones, especially Hop. Although biochemical data define the Hop-mediated Hsp70-Hsp90 substrate transfer mechanism, the intrinsic flexibility of these proteins and the dynamic nature of their complexes have limited the structural studies of this mechanism. Here we generate several complexes in the Hsp70/Hsp90 folding pathway (Hsp90:Hop, Hsp90:Hop:Hsp70 and Hsp90:Hop:Hsp70 with a fragment of the client protein glucocorticoid receptor (GR-LBD)), and determine their 3D structure using electron microscopy techniques. Our results show that one Hop molecule binds to one side of the Hsp90 dimer in both extended and compact conformations, through Hop domain rearrangement that take place when Hsp70 or Hsp70:GR-LBD bind to Hsp90:Hop. The compact conformation of the Hsp90:Hop:Hsp70:GR-LBD complex shows that GR-LBD binds to the side of the Hsp90 dimer opposite the Hop attachment site.
在真核生物中，伴侣蛋白 Hsp70 和 Hsp90 在几种共伴侣蛋白（尤其是 Hop）的帮助下协调作用于一系列关键蛋白的折叠和成熟。尽管生化数据定义了 Hop 介导的 Hsp70-Hsp90 底物转移机制，但这些蛋白质的固有灵活性及其复合物的动态性质限制了对该机制的结构研究。在这里，我们在 Hsp70/Hsp90 折叠途径中生成了几个复合物（Hsp90:Hop、Hsp90:Hop:Hsp70 和 Hsp90:Hop:Hsp70 与糖皮质激素受体 (GR-LBD) 的片段），并使用电子显微镜技术确定了它们的 3D 结构。我们的结果表明，在 Hsp70 或 Hsp70:GR-LBD 与 Hsp90:Hop 结合时，Hop 分子通过发生的 Hop 结构域重排，以伸展和紧凑构象结合到 Hsp90 二聚体的一侧。Hsp90:Hop:Hsp70:GR-LBD 复合物的紧凑构象表明，GR-LBD 结合到与 Hop 附着位点相对的 Hsp90 二聚体侧。
