Self-assembly of minimal COPII cages.
The small G-protein Sar1 and the cytosolic complexes Sec23/24 and Sec13/31 associate sequentially on endoplasmic reticulum membranes to form a protein coat named COPII, which drives the formation of transport vesicles. Using dynamic light scattering, we show that Sec23/24 and Sec13/31 can self-assemble in a stoichiometric manner in solution to form particles with hydrodynamic radii in the range of 40-60 nm. Self-assembly is favoured by lowering the pH, the ionic strength and/or the temperature. Electron microscopy reveals the formation of spherical particles 60-120 nm in diameter with a tight, rough mesh on their surfaces. We suggest that these structures, which represent a minimal COPII cage, mimic the molecular organization of the membrane-associated COPII coat.
Antonny
Bruno
B
Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Valbonne, France. antonny@ipmc.cnrs.fr
Gounon
Pierre
P
Schekman
Randy
R
Orci
Lelio
L
D022181:COP-Coated Vesicles / Q000378:metabolism* / Q000648:ultrastructure*; D002352:Carrier Proteins / Q000378:metabolism / Q000648:ultrastructure; D002966:Clathrin / Q000378:metabolism / Q000648:ultrastructure; D020690:GTPase-Activating Proteins; D007700:Kinetics; D008027:Light; D008565:Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D028861:Nuclear Pore Complex Proteins; D049294:Phospholipid Transfer Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000648:ultrastructure; D012542:Scattering, Radiation
D002352:Carrier Proteins; D002966:Clathrin; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D049294:Phospholipid Transfer Proteins; C079620:SEC13 protein, S cerevisiae; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins