Cell
Volume 184, Issue 14, 8 July 2021, Pages 3674-3688.e18
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Article
PspA adopts an ESCRT-III-like fold and remodels bacterial membranes

https://doi.org/10.1016/j.cell.2021.05.042Get rights and content
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Highlights

  • Cryo-EM structure of assembled helical PspA rods

  • PspA adopts a canonical ESCRT-III fold

  • PspA rods can enclose lipids generating positive membrane curvature

  • PspA remodels bacterial membranes following fusion and fission events

Summary

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.

Keywords

PspA
IM30
Vipp1
ESCRT-III
helical reconstruction
cryo-EM
membrane remodeling
cryo-ET
membrane fusion
membrane fission
membrane tubulation

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