Sec24p and Sec16p cooperate to regulate the GTP cycle of the COPII coat

Leslie F. Kung, Silvere Pagant, Eugene Futai, Jennifer G. D'Arcangelo, Roy Buchanan, John C. Dittmar, Robert J.D. Reid, Rodney Rothstein, Susan Hamamoto, Erik L. Snapp, Randy Schekman, Elizabeth A. Miller

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Vesicle budding from the endoplasmic reticulum (ER) employs a cycle of GTP binding and hydrolysis to regulate assembly of the COPII coat. We have identified a novel mutation (sec24-m11) in the cargo-binding subunit, Sec24p, that specifically impacts the GTP-dependent generation of vesicles in vitro. Using a high-throughput approach, we defined genetic interactions between sec24-m11 and a variety of trafficking components of the early secretory pathway, including the candidate COPII regulators, Sed4p and Sec16p. We defined a fragment of Sec16p that markedly inhibits the Sec23p-and Sec31p-stimulated GTPase activity of Sar1p, and demonstrated that the Sec24p-m11 mutation diminished this inhibitory activity, likely by perturbing the interaction of Sec24p with Sec16p. The consequence of the heightened GTPase activity when Sec24p-m11 is present is the generation of smaller vesicles, leading to accumulation of ER membranes and more stable ER exit sites. We propose that association of Sec24p with Sec16p creates a novel regulatory complex that retards the GTPase activity of the COPII coat to prevent premature vesicle scission, pointing to a fundamental role for GTP hydrolysis in vesicle release rather than in coat assembly/disassembly.

Original languageEnglish (US)
Pages (from-to)1014-1027
Number of pages14
JournalEMBO Journal
Issue number4
StatePublished - Feb 15 2012
Externally publishedYes


  • COPII coat
  • intracellular traffic
  • vesicle formation

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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