美国斯坦福大学Judith Frydman等研究人员合作实现人类伴侣蛋白TriC/CCT引导微管蛋白折叠途径的结构可视化。相关论文于2022年12月8日发表在《细胞》杂志上。

为了揭示为什么一些真核生物蛋白只能在TRiC的帮助下折叠，研究人员用人类的prefoldin和TRiC重组了β-微管蛋白的折叠。研究人员发现非结构化的β-微管蛋白被prefoldin传递到开放的TRiC室，然后被ATP依赖的室关闭。冷冻电镜分辨出四个接近原子分辨率的结构，其中包含在封闭的TRiC腔内逐渐折叠的β-微管蛋白中间物，最终形成原生微管蛋白。

这种底物折叠途径似乎受到与TRiC室中保守区域特定位点相互作用的密切指导。TRiC内壁与折叠后的微管蛋白N结构域及其C端E-钩尾之间的初始静电相互作用建立了原生底物拓扑结构，从而使C结构域折叠成为可能。腔内本质上无序的CCT C端促进了微管蛋白核心和中间结构域的后续折叠和GTP的结合。因此，TRiC的腔室提供了化学和拓扑学指令，从而塑造了其专职底物的折叠图谱。

据悉，依赖ATP的环形伴侣蛋白TRiC/CCT对细胞的蛋白稳定至关重要。

附：英文原文

Title: Structural visualization of the tubulin folding pathway directed by human chaperonin TRiC/CCT

Author: Daniel Gestaut, Yanyan Zhao, Junsun Park, Boxue Ma, Alexander Leitner, Miranda Collier, Grigore Pintilie, Soung-Hun Roh, Wah Chiu, Judith Frydman

Issue&Volume: 2022/12/08

Abstract: The ATP-dependent ring-shaped chaperonin TRiC/CCT is essential for cellular proteostasis.To uncover why some eukaryotic proteins can only fold with TRiC assistance, we reconstitutedthe folding of β-tubulin using human prefoldin and TRiC. We find unstructured β-tubulinis delivered by prefoldin to the open TRiC chamber followed by ATP-dependent chamberclosure. Cryo-EM resolves four near-atomic-resolution structures containing progressivelyfolded β-tubulin intermediates within the closed TRiC chamber, culminating in nativetubulin. This substrate folding pathway appears closely guided by site-specific interactionswith conserved regions in the TRiC chamber. Initial electrostatic interactions betweenthe TRiC interior wall and both the folded tubulin N domain and its C-terminal E-hooktail establish the native substrate topology, thus enabling C-domain folding. Intrinsicallydisordered CCT C termini within the chamber promote subsequent folding of tubulin’score and middle domains and GTP-binding. Thus, TRiC’s chamber provides chemical andtopological directives that shape the folding landscape of its obligate substrates.

DOI: 10.1016/j.cell.2022.11.014

Source: https://www.cell.com/cell/fulltext/S0092-8674(22)01457-X