Morizono Marc A, McGuire Kelly L, Birouty Natalie I, Herzik Mark A
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
Nat Commun. 2024 Dec 30;15(1):10815. doi: 10.1038/s41467-024-54499-1.
Maintenance of protein homeostasis is necessary for cell viability and depends on a complex network of chaperones and co-chaperones, including the heat-shock protein 70 (Hsp70) system. In human mitochondria, mitochondrial Hsp70 (mortalin) and the nucleotide exchange factor (GrpEL1) work synergistically to stabilize proteins, assemble protein complexes, and facilitate protein import. However, our understanding of the molecular mechanisms guiding these processes is hampered by limited structural information. To elucidate these mechanistic details, we used cryoEM to determine structures of full-length human mortalin-GrpEL1 complexes in previously unobserved states. Our structures and molecular dynamics simulations allow us to delineate specific roles for mortalin-GrpEL1 interfaces and to identify steps in GrpEL1-mediated nucleotide and substrate release by mortalin. Subsequent analyses reveal conserved mechanisms across bacteria and mammals and facilitate a complete understanding of sequential nucleotide and substrate release for the Hsp70 chaperone system.
维持蛋白质稳态对于细胞活力至关重要，且依赖于包括热休克蛋白70（Hsp70）系统在内的伴侣蛋白和共伴侣蛋白组成的复杂网络。在人类线粒体中，线粒体Hsp70（mortalin）和核苷酸交换因子（GrpEL1）协同作用以稳定蛋白质、组装蛋白质复合物并促进蛋白质导入。然而，有限的结构信息阻碍了我们对指导这些过程的分子机制的理解。为了阐明这些机制细节，我们使用冷冻电镜来确定全长人类mortalin - GrpEL1复合物处于先前未观察到的状态下的结构。我们的结构和分子动力学模拟使我们能够描绘mortalin - GrpEL1界面的特定作用，并确定GrpEL1介导的mortalin核苷酸和底物释放的步骤。后续分析揭示了细菌和哺乳动物之间的保守机制，并有助于全面理解Hsp70伴侣蛋白系统中核苷酸和底物的顺序释放。
