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1: Biochemistry. 2007 Nov 13;46(45):13041-8. Epub 2007 Oct 23.
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Structure of human synaptotagmin 1 C2AB in the absence of Ca2+ reveals a novel domain association.

Fuson KL, Montes M, Robert JJ, Sutton RB.

Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.

Release of neurotransmitter from synaptic vesicles requires the Ca2+/phospholipid-binding protein synaptotagmin 1. There is considerable evidence that cooperation between the tandem C2 domains of synaptotagmin is a requirement of regulated exocytosis; however, high-resolution structural evidence for this interaction has been lacking. The 2.7 A crystal structure of the cytosolic domains of human synaptotagmin 1 in the absence of Ca2+ reveals a novel closed conformation of the protein. The shared interface between C2A and C2B is stabilized by a network of interactions between residues on the C-terminal alpha-helix of the C2B domain and residues on loops 1-3 of the Ca2+-binding region of C2A. These interactions alter the overall shape of the Ca2+-binding pocket of C2A, but not that of C2B. Thus, synaptotagmin 1 C2A-C2B may utilize a novel regulatory mechanism whereby one C2 domain could regulate the other until an appropriate triggering event decouples them.

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PMID: 17956130 [PubMed - indexed for MEDLINE]