Fig. 4.
(A) SNARE motifs in trans complexes are essential for membrane fusion. Shown is the number of fusing v-liposomes as percentage of all v-liposomes at the target membrane within the first 50 s of video streaming before addition of divalent cations or within 50 s after the addition of divalent cations. Error values represent SEM. (B) More than 50% of fusion-competent v-liposomes fuse within 10 s after Ca2+ addition. The bars represent means ± SEM of normalized values for eight independent experiments (total of 696 fusion events); the final Ca2+ concentration was 100 μM. (B Inset) The onset of Ca2+-evoked fusion is fast. Using dual-color TIR-FM, the emission of Fluo-5N and Rh-DPPE-labeled v-liposomes was recorded simultaneously. Ca2+ was added after recording times >10 s to establish baseline behavior. The plot shown is representative of four experiments. The final Ca2+ concentration used was 200 μM.