SNARE complex formation is triggered by Ca2+ and drives membrane fusion

Cell. 1999 Apr 16;97(2):165-74. doi: 10.1016/s0092-8674(00)80727-8.


Neurotransmitter exocytosis, a process mediated by a core complex of syntaxin, SNAP-25, and VAMP (SNAREs), is inhibited by SNARE-cleaving neurotoxins. Botulinum neurotoxin E inhibition of norepinephrine release in permeabilized PC12 cells can be rescued by adding a 65 aa C-terminal fragment of SNAP-25 (S25-C). Mutations along the hydrophobic face of the S25-C helix result in SNARE complexes with different thermostabilities, and these mutants rescue exocytosis to different extents. Rescue depends on the continued presence of both S25-C and Ca2+ and correlates with complex formation. The data suggest that Ca2+ triggers S25-C binding to a low-affinity site, initiating trans-complex formation. Pairing of SNARE proteins on apposing membranes leads to bilayer fusion and results in a high-affinity cis-SNARE complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Botulinum Toxins / toxicity
  • Calcium / metabolism*
  • DNA Primers / genetics
  • Exocytosis / drug effects
  • Exocytosis / physiology
  • Macromolecular Substances
  • Membrane Fusion / physiology*
  • Membrane Proteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • Mutation
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • PC12 Cells
  • Rats
  • SNARE Proteins
  • Synaptosomal-Associated Protein 25
  • Vesicular Transport Proteins*


  • DNA Primers
  • Macromolecular Substances
  • Membrane Proteins
  • Nerve Tissue Proteins
  • SNARE Proteins
  • Snap25 protein, mouse
  • Snap25 protein, rat
  • Synaptosomal-Associated Protein 25
  • Vesicular Transport Proteins
  • Botulinum Toxins
  • Calcium
  • botulinum toxin type E