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Abstract：
PspA is the main effector of the phage shock protein (Psp) system and preserves the bacterial inner membrane integrity and function. Here, we present the 3.6 Å resolution cryoelectron microscopy (cryo-EM) structure of PspA assembled in helical rods. PspA monomers adopt a canonical ESCRT-III fold in an extended open conformation. PspA rods are capable of enclosing lipids and generating positive membrane curvature. Using cryo-EM, we visualized how PspA remodels membrane vesicles into μm-sized structures and how it mediates the formation of internalized vesicular structures. Hotspots of these activities are zones derived from PspA assemblies, serving as lipid transfer platforms and linking previously separated lipid structures. These membrane fusion and fission activities are in line with the described functional properties of bacterial PspA/IM30/LiaH proteins. Our structural and functional analyses reveal that bacterial PspA belongs to the evolutionary ancestry of ESCRT-III proteins involved in membrane remodeling.
摘要：
PspA是噬菌体休克蛋白（Psp）系统的主要效应子，保持细菌内膜的完整性和功能。这里,我们介绍了组装在螺旋杆中的PspA的3.6µ分辨率低温电子显微镜（cryo-EM）结构。PspA单体以扩展的开放构象采用规范的ESCRT-III折叠。PspA棒能够封闭脂质并产生正膜曲率。使用低温EM，我们可视化了PspA如何将膜囊泡重塑为μm大小的结构，以及它如何介导内化囊泡结构的形成。这些活动的热点是来自PspA组件的区域，作为脂质转移平台和连接先前分离的脂质结构。这些膜融合和裂变活性与细菌PspA/IM30/LiaH蛋白的所述功能特性一致。我们的结构和功能分析表明，细菌PspA属于参与膜重塑的ESCRT-III蛋白的进化祖先。
