Dynamics of the COPII coat with GTP and stable analogues.
We have developed an assay to monitor the assembly of the COPII coat onto liposomes in real time. We show that with Sar1pGTP bound to liposomes, a single round of assembly and disassembly of the COPII coat lasts a few seconds. The two large COPII complexes Sec23/24p and Sec13/31p bind almost instantaneously (in less than 1 s) to Sar1pGTP-doped liposomes. This binding is followed by a fast (less than 10 s) disassembly due to a 10-fold acceleration of the GTPase-activating protein activity of Sec23/24p by the Sec13/31p complex. Experiments with the phosphate analogue BeFx suggest that Sec23/24p provides residues directly involved in GTP hydrolysis on Sar1p.
Antonny
B
B
Department of Molecular and Cell Biology, Howard Hugues Medical Institute, Stanley Hall, University of California, Berkeley, California 94720, USA.
Madden
D
D
Hamamoto
S
S
Orci
L
L
Schekman
R
R
D022181:COP-Coated Vesicles / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008081:Liposomes; C079037:SEC23 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D006160:Guanosine Triphosphate; D020559:Monomeric GTP-Binding Proteins; C077395:SAR1 protein, S cerevisiae