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Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly
Author(s) -
Kalyana Sundaram Ramalingam Venkat,
Jin Huaizhou,
Li Feng,
Shu Tong,
Coleman Jeff,
Yang Jie,
Pincet Frederic,
Zhang Yongli,
Rothman James E.,
Krishnakumar Shyam S.
Publication year - 2021
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.14006
Subject(s) - snap25 , snare complex , chemistry , vesicle , vesicle fusion , linker , biophysics , syntaxin , lipid bilayer fusion , förster resonance energy transfer , synaptic vesicle , membrane , biology , biochemistry , computer science , physics , fluorescence , quantum mechanics , operating system
Synaptic vesicle fusion is mediated by SNARE proteins—VAMP2 on the vesicle and Syntaxin‐1/SNAP25 on the presynaptic membrane. Chaperones Munc18‐1 and Munc13‐1 cooperatively catalyze SNARE assembly via an intermediate ‘template’ complex containing Syntaxin‐1 and VAMP2. How SNAP25 enters this reaction remains a mystery. Here, we report that Munc13‐1 recruits SNAP25 to initiate the ternary SNARE complex assembly by direct binding, as judged by bulk FRET spectroscopy and single‐molecule optical tweezer studies. Detailed structure–function analyses show that the binding is mediated by the Munc13‐1 MUN domain and is specific for the SNAP25 ‘linker’ region that connects the two SNARE motifs. Consequently, freely diffusing SNAP25 molecules on phospholipid bilayers are concentrated and bound in ~ 1 : 1 stoichiometry by the self‐assembled Munc13‐1 nanoclusters.