COPII: a membrane coat formed by Sec proteins that drive vesicle budding from the endoplasmic reticulum.
In vitro synthesis of endoplasmic reticulum-derived transport vesicles has been reconstituted with washed membranes and three soluble proteins (Sar1p, Sec13p complex, and Sec23p complex). Vesicle formation requires GTP but can be driven by nonhydrolyzable analogs such as GMP-PNP. However, GMP-PNP vesicles fail to target and fuse with the Golgi complex whereas GTP vesicles are functional. All the cytosolic proteins required for vesicle formation are retained on GMP-PNP vesicles, while Sar1p dissociates from GTP vesicles. Thin section electron microscopy of purified preparations reveals a uniform population of 60-65 nm vesicles with a 10 nm thick electron dense coat. The subunits of this novel coat complex are molecularly distinct from the constituents of the nonclathrin coatomer involved in intra-Golgi transport. Because the overall cycle of budding driven by these two types of coats appears mechanistically similar, we propose that the coat structures be called COPI and COPII.
Barlowe
C
C
Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley 94720.
Orci
L
L
Yeung
T
T
Hosobuchi
M
M
Hamamoto
S
S
Salama
N
N
Rexach
M F
MF
Ravazzola
M
M
Amherdt
M
M
Schekman
R
R
D001483:Base Sequence; D001692:Biological Transport; D022181:COP-Coated Vesicles; D004247:DNA; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D028861:Nuclear Pore Complex Proteins; D015388:Organelles / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; C079620:SEC13 protein, S cerevisiae; C079037:SEC23 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D006160:Guanosine Triphosphate; D004247:DNA; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins; C077395:SAR1 protein, S cerevisiae