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An extended helical conformation in domain 3a of Munc18-1 provides a template for SNARE (Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor) complex assembly

Munc18-1, a SEC1/Munc18 protein and key regulatory protein in synaptic transmission, can either promote or inhibit SNARE complex assembly. Although the binary inhibitory interaction between Munc18-1 and closed syntaxin 1 is well described, the mechanism of how Munc18-1 stimulates membrane fusion rem...

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Main Authors: Parisotto, Daniel (Author) , Pfau, Maximilian (Author) , Malsam, Andrea (Author) , Wild, Klemens (Author) , Mayer, Matthias P. (Author) , Malsam, Jörg (Author) , Sinning, Irmgard (Author) , Söllner, Thomas (Author)
Format: Article (Journal)
Language:English
Published: February 14, 2014
In: The journal of biological chemistry
Year: 2014, Volume: 289, Issue: 14, Pages: 9639-9650
ISSN:1083-351X
DOI:10.1074/jbc.M113.514273
Online Access:Resolving-System, lizenzpflichtig, Volltext: https://doi.org/10.1074/jbc.M113.514273
Verlag, lizenzpflichtig, Volltext: http://www.jbc.org/content/289/14/9639
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Author Notes:Daniel Parisotto, Maximilian Pfau, Andrea Scheutzow, Klemens Wild, Matthias P. Mayer, Jörg Malsam, Irmgard Sinning, and Thomas H. Söllner
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Summary:Munc18-1, a SEC1/Munc18 protein and key regulatory protein in synaptic transmission, can either promote or inhibit SNARE complex assembly. Although the binary inhibitory interaction between Munc18-1 and closed syntaxin 1 is well described, the mechanism of how Munc18-1 stimulates membrane fusion remains elusive. Using a reconstituted assay that resolves vesicle docking, priming, clamping, and fusion during synaptic exocytosis, we show that helix 12 in domain 3a of Munc18-1 stimulates SNAREpin assembly and membrane fusion. A single point mutation (L348R) within helix 12 selectively abolishes VAMP2 binding and the stimulatory function of Munc18-1 in membrane fusion. In contrast, targeting a natural switch site (P335A) at the start of helix 12, which can result in an extended α-helical conformation, further accelerates lipid-mixing. Together with structural modeling, the data suggest that helix 12 provides a folding template for VAMP2, accelerating SNAREpin assembly and membrane fusion. Analogous SEC1/Munc18-SNARE interactions at other transport steps may provide a general mechanism to drive lipid bilayer merger. At the neuronal synapse, Munc18-1 may convert docked synaptic vesicles into a readily releasable pool.
Item Description:Gesehen am 04.09.2020
Physical Description:Online Resource
ISSN:1083-351X
DOI:10.1074/jbc.M113.514273

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