Journal
STRUCTURE
Volume 8, Issue 7, Pages 685-694Publisher
CELL PRESS
DOI: 10.1016/S0969-2126(00)00156-8
Keywords
membrane fusion; neuronal Sec1; neurotransmitter release; squid; X-ray structure
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Background: Sec1-like molecules have been implicated in a Variety of eukaryotic vesicle transport processes including neurotransmitter release by exocytosis. They regulate vesicle transport by binding to a t-SNARE from the syntaxin family. This process is thought to prevent SNARE complex formation, a protein complex required for membrane fusion. Whereas Sec1 molecules are essential for neurotransmitter release and other secretory events, their interaction with syntaxin molecules seems to represent a negative regulatory step in secretion. Results: Here we report the X-ray crystal structure of a neuronal Sec1 homologue from squid, s-Sec1, at 2.4 Angstrom resolution. Neuronal s-Sec1 is a modular protein that folds into a V-shaped three-domain assembly. Peptide and mutagenesis studies are discussed with respect to the mechanism of Sec1 regulation, Comparison of the structure of squid s-Sec1 with the previously determined structure of rat neuronal Sec1 (n-Sec1) bound to syntaxin-1a indicates conformational rearrangements in domain III induced by syntaxin binding. Conclusions: The crystal structure of s-Sec1 provides the molecular scaffold for a number of molecular interactions that have been reported to affect Sec1 function. The structural differences observed between s-Sec1 and the structure of a rat n-Sec1-syntaxin-1a complex suggest that local conformational changes are sufficient to release syntaxin-1a from neuronal Sec1, an active process that is thought to involve additional effector molecule(s).
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