Department of Biochemistry, School of Medicine, University of Utah, 15 N. Medical Drive East, Salt Lake City, UT 84112, USA.
Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA.
Mol Cell. 2023 Nov 2;83(21):3852-3868.e6. doi: 10.1016/j.molcel.2023.09.032. Epub 2023 Oct 17.
The Chaperonin Containing Tailless polypeptide 1 (CCT) complex is an essential protein folding machine with a diverse clientele of substrates, including many proteins with β-propeller domains. Here, we determine the structures of human CCT in complex with its accessory co-chaperone, phosducin-like protein 1 (PhLP1), in the process of folding Gβ, a component of Regulator of G protein Signaling (RGS) complexes. Cryoelectron microscopy (cryo-EM) and image processing reveal an ensemble of distinct snapshots that represent the folding trajectory of Gβ from an unfolded molten globule to a fully folded β-propeller. These structures reveal the mechanism by which CCT directs Gβ folding through initiating specific intermolecular contacts that facilitate the sequential folding of individual β sheets until the propeller closes into its native structure. This work directly visualizes chaperone-mediated protein folding and establishes that CCT orchestrates folding by stabilizing intermediates through interactions with surface residues that permit the hydrophobic core to coalesce into its folded state.
无尾肽 1 (CCT) 包含的伴侣蛋白复合物是一种重要的蛋白质折叠机器，具有多样化的底物客户群，包括许多具有β-螺旋桨结构域的蛋白质。在这里，我们确定了人 CCT 与其辅助共伴侣蛋白 PhLP1 结合折叠 Gβ的结构，Gβ是 G 蛋白信号调节因子（RGS）复合物的一个组成部分。冷冻电镜（cryo-EM）和图像处理揭示了一系列不同的快照，代表了 Gβ从无规卷曲到完全折叠的β-螺旋桨的折叠轨迹。这些结构揭示了 CCT 通过起始特定的分子间相互作用来指导 Gβ折叠的机制，这些相互作用促进了各个β片层的顺序折叠，直到推进器折叠成其天然结构。这项工作直接可视化了伴侣蛋白介导的蛋白质折叠，并证实了 CCT 通过与表面残基的相互作用来稳定中间体，从而协调折叠，允许疏水区合并到其折叠状态。
