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

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

Author information

1
Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States.
2
Departments of Biochemistry, University of Washington, Seattle, United States.
3
Department of Physiology and Biophysics, University of Washington, Seattle, United States.

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

PMID:
28718762
PMCID:
PMC5540461
DOI:
10.7554/eLife.26646
[Indexed for MEDLINE]
Free PMC Article

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