WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium.
Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Structural and Molecular Microbiology, Structural Biology Research Center, VIB, 1050 Brussels, Belgium.
Cell. 2023 Mar 2;186(5):1039-1049.e17. doi: 10.1016/j.cell.2023.01.013. Epub 2023 Feb 9.
Hsp60 chaperonins and their Hsp10 cofactors assist protein folding in all living cells, constituting the paradigmatic example of molecular chaperones. Despite extensive investigations of their structure and mechanism, crucial questions regarding how these chaperonins promote folding remain unsolved. Here, we report that the bacterial Hsp60 chaperonin GroEL forms a stable, functionally relevant complex with the chaperedoxin CnoX, a protein combining a chaperone and a redox function. Binding of GroES (Hsp10 cofactor) to GroEL induces CnoX release. Cryoelectron microscopy provided crucial structural information on the GroEL-CnoX complex, showing that CnoX binds GroEL outside the substrate-binding site via a highly conserved C-terminal α-helix. Furthermore, we identified complexes in which CnoX, bound to GroEL, forms mixed disulfides with GroEL substrates, indicating that CnoX likely functions as a redox quality-control plugin for GroEL. Proteins sharing structural features with CnoX exist in eukaryotes, suggesting that Hsp60 molecular plugins have been conserved through evolution.
Hsp60 伴侣蛋白及其 Hsp10 辅助因子协助所有活细胞中的蛋白质折叠，构成了分子伴侣的典型范例。尽管对其结构和机制进行了广泛的研究，但关于这些伴侣蛋白如何促进折叠的关键问题仍未得到解决。在这里，我们报告细菌 Hsp60 伴侣蛋白 GroEL 与 chaperedoxin CnoX 形成稳定的、具有功能相关性的复合物，CnoX 是一种结合了伴侣蛋白和氧化还原功能的蛋白质。GroES（Hsp10 辅助因子）与 GroEL 的结合诱导 CnoX 的释放。冷冻电子显微镜为 GroEL-CnoX 复合物提供了关键的结构信息，显示 CnoX 通过高度保守的 C 末端α-螺旋结合到 GroEL 外部的底物结合位点。此外，我们还鉴定了 CnoX 与 GroEL 结合的复合物，其中 CnoX 与 GroEL 底物形成混合二硫键，表明 CnoX 可能作为 GroEL 的氧化还原质量控制插件发挥作用。与 CnoX 具有结构特征的蛋白质存在于真核生物中，这表明 Hsp60 分子插件在进化过程中得到了保守。
