Sec17/Sec18 act twice, enhancing membrane fusion and then disassembling cis-SNARE complexes

Elife. 2017 Jul 18:6:e26646. doi: 10.7554/eLife.26646.

Abstract

At physiological protein levels, the slow HOPS- and SNARE-dependent fusion which occurs upon complete SNARE zippering is stimulated by Sec17 and Sec18:ATP without requiring ATP hydrolysis. To stimulate, Sec17 needs its central residues which bind the 0-layer of the SNARE complex and its N-terminal apolar loop. Adding a transmembrane anchor to the N-terminus of Sec17 bypasses this requirement for apolarity of the Sec17 loop, suggesting that the loop functions for membrane binding rather than to trigger bilayer rearrangement. In contrast, when complete C-terminal SNARE zippering is prevented, fusion strictly requires Sec18 and Sec17, and the Sec17 apolar loop has functions beyond membrane anchoring. Thus Sec17 and Sec18 act twice in the fusion cycle, binding to trans-SNARE complexes to accelerate fusion, then hydrolyzing ATP to disassemble cis-SNARE complexes.

Keywords: S. cerevisiae; SNAREs; Sec17/aSNAP; Sec18/NSF; biochemistry; cell biology; membrane fusion; yeast vacuoles.

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism*
  • Biological Transport
  • Lipid Bilayers / chemistry
  • Lipid Bilayers / metabolism
  • Membrane Fusion*
  • Protein Binding
  • Proteolipids / chemistry
  • Proteolipids / metabolism*
  • SNARE Proteins / chemistry
  • SNARE Proteins / metabolism*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins / chemistry
  • Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins / metabolism*
  • Vacuoles / metabolism
  • Vesicular Transport Proteins / chemistry
  • Vesicular Transport Proteins / metabolism*

Substances

  • Lipid Bilayers
  • Proteolipids
  • SEC17 protein, S cerevisiae
  • SNARE Proteins
  • Saccharomyces cerevisiae Proteins
  • Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins
  • Vesicular Transport Proteins
  • proteoliposomes
  • Adenosine Triphosphatases
  • SEC18 protein, S cerevisiae