title: Different states of synaptotagmin regulate evoked versus spontaneous release.
abstract: The tandem C2-domains of synaptotagmin 1 (syt) function as Ca(2+)-binding modules that trigger exocytosis; in the absence of Ca(2+), syt inhibits spontaneous release. Here, we used proline linkers to constrain and alter the relative orientation of these C2-domains. Short poly-proline helices have a period of three, so large changes in the relative disposition of the C2-domains result from changing the length of the poly-proline linker by a single residue. The length of the linker was varied one residue at a time, revealing a periodicity of three for the ability of the linker mutants to interact with anionic phospholipids and drive evoked synaptic transmission; syt efficiently drove exocytosis when its tandem C2-domains pointed in the same direction. Analysis of spontaneous release revealed a reciprocal relationship between the activation and clamping activities of the linker mutants. Hence, different structural states of syt underlie the control of distinct forms of synaptic transmission.
authors.affiliation: Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Hua
authors.identifier: http://orcid.org/0000-0002-0448-4052
authors.initials: H
authors.lastname: Bai
authors.affiliation: Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Renhao
authors.initials: R
authors.lastname: Xue
authors.affiliation: Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Huan
authors.initials: H
authors.lastname: Bao
authors.affiliation: Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Leili
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Arun
authors.initials: A
authors.lastname: Yethiraj
authors.affiliation: Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Cui
authors.affiliation: Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Edwin R
authors.initials: ER
authors.lastname: Chapman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D018345:Mice, Knockout; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D009154:Mutation; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011392:Proline / Q000737:chemistry; D017434:Protein Structure, Tertiary; D051381:Rats; D009435:Synaptic Transmission; D050863:Synaptotagmin I / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D018377:Neurotransmitter Agents; D050863:Synaptotagmin I; D011392:Proline