Dae-Hyuk Kweon1, Chang Sup Kim1,2 & Yeon-Kyun Shin1
1Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA.
2Present address: Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, South Korea.
In the neuron, SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors)
assembly acts centrally in driving membrane fusion, a required process for neurotransmitter release. In the
cytoplasm, vesicular SNARE VAMP-2 (vesicle-associated membrane protein-2) engages with two plasma membrane
SNAREs, syntaxin 1A and SNAP-25 (synaptosome-associated protein of 25 kDa), to form the core complex that
bridges two membranes. Although various factors regulate SNARE assembly, the membrane also aids in regulation
by trapping VAMP-2 in the membrane. Fluorescence and EPR analyses revealed that the insertion of seven
C-terminal core-forming residues into the membrane controls complex formation of the entire core region, even
though the preceding 54 core-forming residues are fully exposed and freely moving. When two interfacial
tryptophan residues in this region were replaced with hydrophilic serine residues, the mutation supported rapid
complex formation. The results suggest that the membrane-proximal region of VAMP-2 is a regulatory module for
SNARE assembly, providing new insights into calcium-triggered membrane fusion.
Correspondence should be addressed to Y -K Shin.