Membrane remodeling and repair are essential for all cells. Proteins that perform these functions include Vipp1/IM30 in photosynthetic plastids, PspA in bacteria, and ESCRT-III in eukaryotes. Here, using a combination of evolutionary and structural analyses, we show that these protein families are homologous and share a common ancient evolutionary origin that likely predates the last universal common ancestor. This homology is evident in cryo-electron microscopy structures of Vipp1 rings from the cyanobacterium Nostoc punctiforme presented over a range of symmetries. Each ring is assembled from rungs that stack and progressively tilt to form dome-shaped curvature. Assembly is facilitated by hinges in the Vipp1 monomer, similar to those in ESCRT-III proteins, which allow the formation of flexible polymers. Rings have an inner lumen that is able to bind and deform membranes. Collectively, these data suggest conserved mechanistic principles that underlie Vipp1, PspA, and ESCRT-III-dependent membrane remodeling across all domains of life.
Bibliographical noteFunding Information:
We thank Diamond for access and support of the cryo-EM facilities at the UK National Electron Bio-Imaging Centre (eBIC) funded by the Wellcome Trust , MRC , and BBSRC . We thank Paul Simpson for in-house EM support. We thank Jan Löwe for acting as collaboration catalyst. We thank BBSRC for a doctoral training program PhD to O.B. T.A.W. is supported by a Royal Society University Research Fellowship ( UF140626 ). This work was funded by a Wellcome Trust Senior Research Fellowship ( 215553/Z/19/Z ) and previously by a Wellcome Trust Career Development Fellowship ( 200074/Z/15/Z ) to H.H.L. This work was also funded by Wellcome Trust funding to B.B., which supported D.P.S. ( 203276/Z/16/Z ), and via MRC support for the Baum team.
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