Specific SNARE complex binding mode of the Sec1/Munc-18 protein, Sec1p

John Togneri, Yi Shan Cheng, Mary Munson, Frederick M. Hughson, Chavela M. Carr

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

The Sec1/Munc-18 (SM) family of proteins is required for vesicle fusion in eukaryotic cells and has been linked to the membrane-fusion proteins known as soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). SM proteins may activate the target-membrane SNARE, syntaxin, for assembly into the fusogenic SNARE complex. In support of an activation role, SM proteins bind directly to their cognate syntaxins. An exception is the yeast Sec1p, which does not bind the yeast plasma-membrane syntaxin, Sso1p. This exception could be explained if the SM interaction motif were blocked by the highly stable closed conformation of Sso1p. We tested the possibility of a latent binding motif using sso1 mutants in yeast and reconstituted the Sec1p binding specificity observed in vivo with purified proteins in vitro. Our results indicate there is no latent binding motif in Sso1p. Instead, Sec1p binds specifically to the ternary SNARE complex, with no detectable binding to the binary t-SNARE complex or any of the three individual SNAREs in their uncomplexed forms. We propose that vesicle fusion requires a specific interaction between the SM protein and the ternary SNARE complex.

Original languageEnglish (US)
Pages (from-to)17730-17735
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number47
DOIs
StatePublished - Nov 21 2006

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Membrane fusion
  • Sec9p
  • Snc2p
  • Sso1p
  • Syntaxin

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