A coiled coil trigger site is essential for rapid binding of synaptobrevin to the SNARE acceptor complex.
Exocytosis from synaptic vesicles is driven by stepwise formation of a tight alpha-helical complex between the fusing membranes. The complex is composed of the three SNAREs: synaptobrevin 2, SNAP-25, and syntaxin 1a. An important step in complex formation is fast binding of vesicular synaptobrevin to the preformed syntaxin 1.SNAP-25 dimer. Exactly how this step relates to neurotransmitter release is not well understood. Here, we combined different approaches to gain insights into this reaction. Using computational methods, we identified a stretch in synaptobrevin 2 that may function as a coiled coil "trigger site." This site is also present in many synaptobrevin homologs functioning in other trafficking steps. Point mutations in this stretch inhibited binding to the syntaxin 1.SNAP-25 dimer and slowed fusion of liposomes. Moreover, the point mutations severely inhibited secretion from chromaffin cells. Altogether, this demonstrates that the trigger site in synaptobrevin is crucial for productive SNARE zippering.
Wiederhold
Katrin
K
Research Group Structural Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Kloepper
Tobias H
TH
Walter
Alexander M
AM
Stein
Alexander
A
Kienle
Nickias
N
Sørensen
Jakob B
JB
Fasshauer
Dirk
D
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D002151:Calorimetry / Q000379:methods; D019439:Chromaffin Cells / Q000378:metabolism; D019281:Dimerization; D004594:Electrophysiology / Q000379:methods; D008081:Liposomes / Q000737:chemistry; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D050683:R-SNARE Proteins / Q000737:chemistry*; D051381:Rats; D050600:SNARE Proteins / Q000737:chemistry*
D008081:Liposomes; D018377:Neurotransmitter Agents; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D002118:Calcium
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