Nature Cell Biology
3, 531 - 537 (2001)
Published online: 1 May 2001; | doi:10.1038/35078500
Dynamics of the COPII coat with GTP and stable analoguesBruno Antonny1, 3, David Madden1, Susan Hamamoto1, Lelio Orci2
& Randy Schekman11
Department of Molecular and Cell Biology, Howard Hugues Medical Institute, Stanley Hall, University of California, Berkeley, California 94720, USA
2
Département de morphologie, Université de Genève, Centre Médical Universitaire, 1 Rue Michel Servet, Genève 4, CH12-11, Suisse
3
Current address: IPMC−CNRS, 660 route des Lucioles, 06560 Valbonne, France
Correspondence should be addressed to Randy Schekman schekman@uclink4.berkeley.eduWe 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.
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