Understanding the function of Vps1 in membrane remodeling

Abstract

Vacuolar protein sorting (Vps1) is a yeast-specific, multi-domain large GTPase that belongs to the dynamin superfamily of proteins. Vps1 is involved in protein-sorting and the biogenesis of vacuoles, endocytosis as well as the division of peroxisomes. Despite these insights, little is known about its lipid-binding specificity and whether it can facilitate membrane remodeling, which is required to generate transport vesicles or orchestrate organelle division. Here, using biochemical approaches, we elucidate the intrinsic function of the protein in a cell-free system. Vps1 was purified to apparent homogeneity from a bacterial heterologous expression system. Purified Vps1 shows preferential binding to phosphatidylinositol-3-phosphate (PI(3)) and phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) among phosphoinositides and to cardiolipin (CL) among anionic phospholipids. Binding to liposomes containing these lipids results in stimulation of its GTPase activity. Using templates of supported membrane nanotubes that mimic the necks of budded transport vesicles and tubular peroxisomes, we find that Vps1 can catalyze fission of PI(3)P- and PI(4,5)P2-containing membranes but fails to do so on CL-containing membranes. To the best of our knowledge, this constitutes the first report demonstrating membrane fission by Vps1 and that fission is lipid-specific.