FIGURE 3.
Mutations in the trigger site greatly decrease the efficiency of synaptobrevin in mediating liposome fusion. Previously, we showed that SNARE-driven liposome fusion can be greatly accelerated when a purified ΔN complex (SyxH3TMR·SNAP-25·Syb49–96) is used in one population of liposomes. This complex serves as an available acceptor site for liposomes containing synaptobrevin (13, 14, 23, 34–36). Fusion was monitored by lipid dequenching. At a final protein concentration of ∼200 nm for both liposome populations, the liposomes containing wild-type synaptobrevin fused very rapidly, whereas fusion in the presence of the double mutant SybTMRI45A,M46A was much slower.