Zhang Huaqun, Amick Joseph, Chakravarti Ritu, Santarriaga Stephanie, Schlanger Simon, McGlone Cameron, Dare Michelle, Nix Jay C, Scaglione K Matthew, Stuehr Dennis J, Misra Saurav, Page Richard C
Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
Structure. 2015 Mar 3;23(3):472-482. doi: 10.1016/j.str.2015.01.003. Epub 2015 Feb 12.
The ubiquitin ligase CHIP plays an important role in cytosolic protein quality control by ubiquitinating proteins chaperoned by Hsp70/Hsc70 and Hsp90, thereby targeting such substrate proteins for degradation. We present a 2.91 Å resolution structure of the tetratricopeptide repeat (TPR) domain of CHIP in complex with the α-helical lid subdomain and unstructured tail of Hsc70. Surprisingly, the CHIP-TPR interacts with determinants within both the Hsc70-lid subdomain and the C-terminal PTIEEVD motif of the tail, exhibiting an atypical mode of interaction between chaperones and TPR domains. We demonstrate that the interaction between CHIP and the Hsc70-lid subdomain is required for proper ubiquitination of Hsp70/Hsc70 or Hsp70/Hsc70-bound substrate proteins. Posttranslational modifications of the Hsc70 lid and tail disrupt key contacts with the CHIP-TPR and may regulate CHIP-mediated ubiquitination. Our study shows how CHIP docks onto Hsp70/Hsc70 and defines a bipartite mode of interaction between TPR domains and their binding partners.
泛素连接酶CHIP通过对由Hsp70/Hsc70和Hsp90伴侣的蛋白质进行泛素化，在胞质蛋白质质量控制中发挥重要作用，从而将此类底物蛋白靶向降解。我们展示了CHIP的四肽重复（TPR）结构域与Hsc70的α-螺旋盖亚结构域和无结构尾巴形成复合物的2.91 Å分辨率结构。令人惊讶的是，CHIP-TPR与Hsc70盖亚结构域和尾巴的C末端PTIEEVD基序内的决定簇相互作用，呈现出伴侣蛋白与TPR结构域之间非典型的相互作用模式。我们证明，CHIP与Hsc70盖亚结构域之间的相互作用对于Hsp70/Hsc70或与Hsp70/Hsc70结合的底物蛋白的正确泛素化是必需的。Hsc70盖子和尾巴的翻译后修饰破坏了与CHIP-TPR的关键接触，并可能调节CHIP介导的泛素化。我们的研究展示了CHIP如何停靠在Hsp70/Hsc70上，并定义了TPR结构域与其结合伙伴之间的二分相互作用模式。
