Thylakoid membrane remodeling by VIPP1 ESCRT-III-like filaments

Abstract

Three papers show that Vipp1, a plastid ESCRT-III protein, can form sheets, spirals and regular polygons on flat membranes and tubulate the membranes within stacked rings and helices. This work provides a framework for how Vipp1 can deliver lipids for thylakoid membrane biogenesis and protect and repair the membranes during photosynthesis.

Fig. 1 |. Plausible Vipp1 remodeling activities in thylakoid membrane biogenesis, protection and repair.

The figure depicts different possible roles for Vipp1 in thylakoid membrane remodeling. Coils and lines represent Vipp1 protofilaments, arrows depict directions of membrane growth or delivery, and labels define the different processes being highlighted.

Fig. 2 |. Vipp1 structure and assemblies.

a, Vipp1 monomers exhibit a canonical ESCRT-III subunit fold. b, Vipp1 protofilaments are created from interlocking Vipp1 monomers. c,d, Vipp1 protofilaments can curve to form helices (c) or stacked rings (d) that can encase internal membranes. Individual subunits are shown in red. e, Model for how a spiraling Vipp1 filament, comprising protofilaments, can initiate membrane tubulation by twisting to transition from a 2D planar structure into a curved 3D structure that retains the same membrane binding surfaces and protofilament architectures. The twisting protofilaments can ultimately form stacked rings or helices around tubulated membranes (not shown). The membrane binding helix α0 is shown in light purple (and extended for clarity), and helix α4 was removed for clarity. Figures were generated in PyMOL version 2.5.7 using PDB 8QBW (a–c) and PDB 6ZVS (d).