Juxtamembrane tryptophans of synaptobrevin 2 control the process of membrane fusion
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Updated: May 16, 2026

Analysis of SNARE-mediated Membrane Fusion Using an Enzymatic Cell Fusion Assay
Published on: October 19, 2012
Qinghua Fang1, Ying Zhao, Manfred Lindau
1School of Applied & Engineering Physics, Cornell University, Ithaca, NY 14853, USA. fangqinghua@gmail.com
Abstract:
Synaptobrevin 2 (Syb2), syntaxin (Sx1A), and SNAP-25, generate a force to induce fusion pore formation. The v-SNARE, Syb2, is anchored to the vesicle membrane by a single transmembrane domain. Here we show that 2 tryptophans (W89/W90) located in the juxtamembrane domain of Syb2, which stabilize the transmembrane (TM) domain position, control the ratio of spontaneous vs. stimulated membrane fusion events in chromaffin cells. Changing the 2 hydrophobic tryptophans to neutral alanines promotes spontaneous membrane fusion, faster transmitter release kinetics and complete release from individual vesicles. The results indicate that the two tryptophans act as a fusion clamp making fusion stimulus-dependent.
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