title: Lipid packing sensed by ArfGAP1 couples COPI coat disassembly to membrane bilayer curvature.
abstract: Protein coats deform flat lipid membranes into buds and capture membrane proteins to form transport vesicles. The assembly/disassembly cycle of the COPI coat on Golgi membranes is coupled to the GTP/GDP cycle of the small G protein Arf1. At the heart of this coupling is the specific interaction of membrane-bound Arf1-GTP with coatomer, a complex of seven proteins that forms the building unit of the COPI coat. Although COPI coat disassembly requires the catalysis of GTP hydrolysis in Arf1 by a specific GTPase-activating protein (ArfGAP1), the precise timing of this reaction during COPI vesicle formation is not known. Using time-resolved assays for COPI dynamics on liposomes of controlled size, we show that the rate of ArfGAP1-catalysed GTP hydrolysis in Arf1 and the rate of COPI disassembly increase over two orders of magnitude as the curvature of the lipid bilayer increases and approaches that of a typical transport vesicle. This leads to a model for COPI dynamics in which GTP hydrolysis in Arf1 is organized temporally and spatially according to the changes in lipid packing induced by the coat.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, 660 route des Lucioles, 06560 Valbonne-Sophia-Antipolis, France.
authors.forename: Joëlle
authors.initials: J
authors.lastname: Bigay
authors.forename: Pierre
authors.initials: P
authors.lastname: Gounon
authors.forename: Sylviane
authors.initials: S
authors.lastname: Robineau
authors.forename: Bruno
authors.initials: B
authors.lastname: Antonny
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D022181:COP-Coated Vesicles / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D020755:Coat Protein Complex I / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D007425:Intracellular Membranes / Q000737:chemistry; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D011817:Rabbits; D013997:Time Factors
chemical_list: D020755:Coat Protein Complex I; D020690:GTPase-Activating Proteins; D008051:Lipid Bilayers; D008055:Lipids; D008081:Liposomes; D006160:Guanosine Triphosphate; D020727:ADP-Ribosylation Factors