title: Crystal structure and biophysical properties of a complex between the N-terminal SNARE region of SNAP25 and syntaxin 1a.
abstract: SNARE proteins are required for intracellular membrane fusion. In the neuron, the plasma membrane SNAREs syntaxin 1a and SNAP25 bind to VAMP2 found on neurotransmitter-containing vesicles. These three proteins contain "SNARE regions" that mediate their association into stable tetrameric coiled-coil structures. Syntaxin 1a contributes one such region, designated H3, and SNAP25 contributes two SNARE regions to the fusogenic complex with VAMP2. Syntaxin 1a H3 (syn1aH3) and SNAP25 can form a stable assembly, which can then be bound by VAMP2 to form the full SNARE complex. Here we show that syn1aH3 can also form a stable but kinetically trapped complex with the N-terminal SNARE region of SNAP25 (S25N). The crystal structure of this complex reveals an extended parallel four-helix bundle similar to that of the core SNARE and the syn1aH3-SNAP25 complexes. The inherent ability of syn1aH3 and S25N to associate stably in vitro implies that the intracellular fusion machinery must prevent formation of, or remove, any non-productive complexes. Comparison with the syn1aH3-SNAP25 complex suggests that the linkage of the N- and C-terminal SNAP25 SNARE regions is kinetically advantageous in preventing formation of the non-productive syn1aH3-S25N complex. We also demonstrate that the syn1aH3-S25N complex can be disassembled by alpha-SNAP and N-ethylmaleimide-sensitive factor.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305-5126, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Misura
authors.forename: L C
authors.initials: LC
authors.lastname: Gonzalez
authors.forename: A P
authors.initials: AP
authors.lastname: May
authors.forename: R H
authors.initials: RH
authors.lastname: Scheller
authors.forename: W I
authors.initials: WI
authors.lastname: Weis
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry*; D002352:Carrier Proteins / Q000737:chemistry; D002478:Cells, Cultured; D018360:Crystallography, X-Ray; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D052066:N-Ethylmaleimide-Sensitive Proteins; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D011487:Protein Conformation; D051381:Rats; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
chemical_list: D000954:Antigens, Surface; D002352:Carrier Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050600:SNARE Proteins; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins; C498737:Nsf protein, rat