title: Conformational dynamics of calcium-triggered activation of fusion by synaptotagmin.
abstract: Synaptotagmin triggers rapid exocytosis of neurotransmitters from synaptic vesicles in response to Calcium (Ca(2+)) ions. Here, we use a novel Nanodisc-based system, designed to be a soluble mimetic of the clamped synaptic vesicle-bilayer junction, combined with fluorescence resonance energy transfer (FRET) spectroscopy to monitor the structural relationships among SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor), Synaptotagmin C2 domains, and the lipid bilayer in real time during the Ca(2+)-activation process. We report that Synaptotagmin remains rigidly fixed on the partially assembled SNARE complex with no detectable internal rearrangement of its C2 domains, even as it rapidly inserts into the bilayer. We hypothesize that this straightforward, one-step physical mechanism could explain how this Ca(2+)- sensor rapidly activates neurotransmitter release from the clamped state.
authors: Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut. Electronic address: shyam.krishnakumar@yale.edu.
authors: Shyam S
authors: SS
authors: Krishnakumar
authors: Daniel
authors: D
authors: Kümmel
authors: Sunny J
authors: SJ
authors: Jones
authors: Daniel T
authors: DT
authors: Radoff
authors: Karin M
authors: KM
authors: Reinisch
authors: James E
authors: JE
authors: Rothman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D050825:Synaptosomal-Associated Protein 25 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050863:Synaptotagmin I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; C494209:Snap25 protein, mouse; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; D002118:Calcium