The eukaryotic chaperonin TRiC/CCT plays a major role in assisting the folding of many proteins through an ATP-driven allosteric cycle. Recent structures elucidated by cryo-electron microscopy provide a broad view of the conformations visited at various stages of the chaperonin cycle, including a sequential activation of its subunits in response to nucleotide binding. But we lack a thorough mechanistic understanding of the structure-based dynamics and communication properties that underlie the TRiC/CCT machinery. In this study, we present a computational methodology based on elastic network models adapted to cryo-EM density maps to gain a deeper understanding of the structure-encoded allosteric dynamics of this hexadecameric machine. We have analysed several structures of the chaperonin resolved in different states toward mapping its conformational landscape. Our study indicates that the overall architecture intrinsically favours cooperative movements that comply with the structural variabilities observed in experiments. Furthermore, the individual subunits CCT1-CCT8 exhibit state-dependent sequential events at different states of the allosteric cycle. For example, in the ATP-bound state, subunits CCT5 and CCT4 selectively initiate the lid closure motions favoured by the overall architecture; whereas in the apo form of the heteromer, the subunit CCT7 exhibits the highest predisposition to structural change. The changes then propagate through parallel fluxes of allosteric signals to neighbours on both rings. The predicted state-dependent mechanisms of sequential activation provide new insights into TRiC/CCT intra- and inter-ring signal transduction events.

真核伴侣蛋白 TRiC/CCT 在通过 ATP 驱动的变构循环协助许多蛋白质折叠方面发挥着重要作用。最近通过冷冻电子显微镜阐明的结构提供了伴侣蛋白循环各个阶段所访问的构象的广阔视野，包括其亚基响应于核苷酸结合的顺序激活。但我们对 TRiC/CCT 机制背后的基于结构的动力学和通信特性缺乏透彻的机制理解。在这项研究中，我们提出了一种基于适用于冷冻电镜密度图的弹性网络模型的计算方法，以更深入地了解这种十六进制机器的结构编码变构动力学。我们分析了在不同状态下解析的伴侣蛋白的几种结构，以绘制其构象景观。我们的研究表明，整体架构本质上有利于符合实验中观察到的结构变化的合作运动。此外，各个亚基 CCT1-CCT8 在变构循环的不同状态下表现出状态依赖的顺序事件。例如，在 ATP 结合状态下，亚基 CCT5 和 CCT4 选择性地启动整体架构所青睐的眼睑闭合运动；而在异聚体的 apo 形式中，亚基 CCT7 表现出最高的结构变化倾向。然后，这些变化通过变构信号的并行通量传播到两个环上的邻居。预测的顺序激活的状态依赖机制为 TRiC/CCT 环内和环间信号转导事件提供了新的见解。