Eukaryotic members of the endosome sorting complex required for transport-III (ESCRT-III) family have been shown to form diverse higher-order assemblies. The bacterial phage shock protein A (PspA) has been identified as a member of the ESCRT-III superfamily, and PspA homo-oligomerizes to form rod-shaped assemblies. As observed for eukaryotic ESCRT-III, PspA forms tubular assemblies of varying diameters. Using electron cryo-electron microscopy, we determined 61 Synechocystis PspA structures and observed in molecular detail how the structural plasticity of PspA rods is mediated by conformational changes at three hinge regions in the monomer and by the fixed and changing molecular contacts between protomers. Moreover, we reduced and increased the structural plasticity of PspA rods by removing the loop connecting helices α3/α4 and the addition of nucleotides, respectively. Based on our analysis of PspA-mediated membrane remodeling, we suggest that the observed mode of structural plasticity is a prerequisite for the biological function of ESCRT-III members.

运输-III (ESCRT-III) 家族所需的内体分选复合体的真核成员已被证明可以形成不同的高阶组装体。细菌噬菌体休克蛋白 A (PspA) 已被鉴定为 ESCRT-III 超家族的成员，并且 PspA 同源寡聚化形成杆状组件。正如对真核 ESCRT-III 所观察到的，PspA 形成不同直径的管状组件。使用电子冷冻电子显微镜，我们确定了 61 个集胞藻PspA 结构，并在分子细节中观察了 PspA 杆的结构可塑性如何通过单体中三个铰链区的构象变化以及原聚体之间的固定和变化的分子接触来介导。此外，我们分别通过去除连接螺旋α3/α4的环和添加核苷酸来减少和增加PspA杆的结构可塑性。基于我们对 PspA 介导的膜重塑的分析，我们认为观察到的结构可塑性模式是 ESCRT-III 成员生物学功能的先决条件。