title: Surface structure of the COPII-coated vesicle.
abstract: The spatial arrangement of COPII coat protein subunits was analyzed by crosslinking to an artificial membrane surface and by electron microscopy of coat proteins and coated vesicle surfaces. The efficiency of COPII subunit crosslinking to phospholipids declined in order of protein recruitment to the coat: Sar1p > Sec23/24p >> Sec13/31p. Deep-etch rotary shadowing and electron microscopy were used to explore the COPII subunit structure with isolated proteins and coated vesicles. Sec23/24 resembles a bow tie, and Sec13/31p contains terminal bilobed globular structures bordering a central rod. The surface structure of COPII vesicles revealed a coat built with polygonal units. The length of the side of the hexagonal/pentagonal units is close to the dimension of the central rod-like segment of Sec13/31. Partially uncoated profiles revealed strands of Sec13/31p stripped from the vesicle surface. We conclude that the coat subunits form layers displaced from the membrane surface in reverse order of addition to the coat.
authors.affiliation: Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3206, USA.
authors.forename: K
authors.initials: K
authors.lastname: Matsuoka
authors.forename: R
authors.initials: R
authors.lastname: Schekman
authors.forename: L
authors.initials: L
authors.lastname: Orci
authors.forename: J E
authors.initials: JE
authors.lastname: Heuser
mesh_terms: D022181:COP-Coated Vesicles / Q000378:metabolism / Q000648:ultrastructure*; D002352:Carrier Proteins / Q000378:metabolism / Q000648:ultrastructure*; D002462:Cell Membrane / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism / Q000648:ultrastructure*; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure*; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism / Q000648:ultrastructure; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins / Q000378:metabolism / Q000648:ultrastructure*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D010750:Phosphoproteins; C079620:SEC13 protein, S cerevisiae; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; C106113:SEC31 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D020559:Monomeric GTP-Binding Proteins; C077395:SAR1 protein, S cerevisiae