FIGURE 4.

Tomosyn inhibits the content mixing of SNARE-mediated membrane fusion. A, content mixing of the reconstituted fusion reactions. The v-SNARE liposomes, in which sulforhodamine B was encapsulated, were directed to fuse with unlabeled t-SNARE liposomes in the absence or presence of 5 μm tomosyn. Each fusion reaction contained 5 μm t-SNAREs and 1.5 μm v-SNARE. Data are presented as fluorescence increase over time. In negative controls, 20 μm VAMP2 CD was added to the fusion reactions. B, the leakage controls of the content mixing reactions. Sulforhodamine B was included in both v- and t-SNARE liposomes. Increases in sulforhodamine B fluorescence were not observed, indicating that no detectable content leakage occurred during the fusion reactions. C, initial content mixing rates of the fusion reactions shown in A. Data are presented as percentage of fluorescence change per 10 min. Error bars indicate S.D.