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bioRxiv · 10.1101/2025.06.13.659447

The bacterial ESCRT-III PspA rods thin lipid tubules and and increase membrane curvature through helix α0 interactions

Hudina, E.·Schott-Verdugo, S.·Junglas, B.·Kutzner, M.·Ritter, I.·Hellmann, N.·Schneider, D.·Gohlke, H.·Sachse, C.
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Abstract

The phage shock protein A (PspA), a bacterial member of the ESCRT-III superfamily, forms rod-shaped helical assemblies that internalize membrane tubules. The N-terminal helix 0 of PspA (and other ESCRT-III members) has been suggested to act as a membrane anchor, the detailed mechanism, however, of how it binds to membranes and eventually triggers membrane fusion and/or fission events remains unclear. By solving a total of 15 cryo-electron microscopy (cryo-EM) structures of PspA and a truncation lacking the N-terminal helix 0 in the presence of EPL membranes, we show in molecular detail how PspA interacts with and remodels membranes: binding of the N-terminal helix 0 in the outer tubular membrane leaflet induces membrane curvature, supporting membrane tubulation by PspA. Detailed molecular dynamics simulations and free energy computations of interactions between the helix 0 and negatively charged membranes suggest a compensating mechanism between helix/membrane interactions and the energy contributions required for membrane bending. The energetic considerations are in line with the membrane structures observed in the cryo-EM images of tubulated membrane vesicles, fragmented vesicles inside tapered PspA rods, and shedded vesicles emerging at the thinner PspA rod ends. Our results provide insights into the molecular determinants and a potential mechanism of vesicular membrane remodeling mediated by a member of the ESCRT-III superfamily. SummaryThe rods of bacterial ESCRT-III protein PspA internalize and thin membrane tubules by overcoming the required bending energy through progressive membrane binding of the N-terminal helix in the PspA assembly.

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Hudina, E., Schott-Verdugo, S., Junglas, B., Kutzner, M., Ritter, I., Hellmann, N., Schneider, D., Gohlke, H., Sachse, C.. 2025-06-13. The bacterial ESCRT-III PspA rods thin lipid tubules and and increase membrane curvature through helix α0 interactions. https://doi.org/10.1101/2025.06.13.659447

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