A protein assembly-disassembly pathway in vitro that may correspond to sequential steps of synaptic vesicle docking, activation, and fusion

Cell. 1993 Nov 5;75(3):409-18. doi: 10.1016/0092-8674(93)90376-2.


The SNARE hypothesis holds that a transport vesicle chooses its target for fusion when a soluble NSF attachment protein (SNAP) receptor on the vesicle (v-SNARE) pairs with its cognate t-SNARE at the target membrane. Three synaptosomal membrane proteins have previously been identified: syntaxin, SNAP-25 (t-SNAREs), and vesicle-associated membrane protein (VAMP) (v-SNARE); all assemble with SNAPs and NSF into 20S fusion particles. We now report that in the absence of SNAP and NSF, these three SNAREs form a stable complex that can also bind synaptotagmin. Synaptotagmin is displaced by alpha-SNAP, suggesting that these two proteins share binding sites on the SNARE complex and implying that synaptotagmin operates as a "clamp" to prevent fusion from proceeding in the absence of a signal. The alpha-SNAP-SNARE complex can bind NSF, and NSF-dependent hydrolysis of ATP dissociates the complex, separating syntaxin, SNAP-25, and VAMP. ATP hydrolysis by NSF may provide motion to initiate bilayer fusion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Animals
  • Antigens, Surface / isolation & purification
  • Brain / metabolism
  • Calcium-Binding Proteins*
  • Carrier Proteins / metabolism
  • Cattle
  • Exocytosis
  • Fluorescent Antibody Technique
  • Membrane Fusion*
  • Membrane Glycoproteins / metabolism
  • Membrane Proteins*
  • Models, Biological
  • N-Ethylmaleimide-Sensitive Proteins
  • Nerve Tissue Proteins / isolation & purification
  • Nerve Tissue Proteins / metabolism*
  • PC12 Cells
  • Synaptic Vesicles / metabolism*
  • Synaptosomal-Associated Protein 25
  • Synaptotagmins
  • Syntaxin 1
  • Vesicular Transport Proteins*


  • Antigens, Surface
  • Calcium-Binding Proteins
  • Carrier Proteins
  • Membrane Glycoproteins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Synaptosomal-Associated Protein 25
  • Syntaxin 1
  • Vesicular Transport Proteins
  • Synaptotagmins
  • Adenosine Triphosphatases
  • N-Ethylmaleimide-Sensitive Proteins