Wang Shuxin, Sass Mikaila I, Kwon Yujin, Ludlam W Grant, Smith Theresa M, Carter Ethan J, Gladden Nathan E, Riggi Margot, Iwasa Janet H, Willardson Barry M, Shen Peter S
Department of Biochemistry, 15 N. Medical Drive East, University of Utah, Salt Lake City, UT, 84112, USA.
Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA.
bioRxiv. 2023 May 4:2023.05.04.539424. doi: 10.1101/2023.05.04.539424.
The cytosolic 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 determined structures of 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. Cryo-EM and image processing revealed 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 directs folding by stabilizing intermediates through interactions with surface residues that permit the hydrophobic core to coalesce into its folded state.
胞质无尾多肽1伴侣蛋白复合体（CCT）是一种重要的蛋白质折叠机器，其底物种类多样，包括许多具有β-螺旋桨结构域的蛋白质。在此，我们确定了CCT与其辅助伴侣蛋白——类视紫红质蛋白1（PhLP1）形成的复合体在折叠Gβ（G蛋白信号调节因子复合体的一个组分）过程中的结构。冷冻电镜和图像处理揭示了一系列不同的瞬间结构，这些结构代表了Gβ从未折叠的熔融球状体到完全折叠的β-螺旋桨的折叠轨迹。这些结构揭示了CCT指导Gβ折叠的机制，即通过启动特定的分子间接触来促进单个β-折叠片层的顺序折叠，直至螺旋桨闭合形成其天然结构。这项工作直接可视化了伴侣蛋白介导的蛋白质折叠，并确定CCT通过与表面残基相互作用来稳定中间体从而指导折叠，这些表面残基使疏水核心聚合成其折叠状态。
