Fig. 4. Reconstitution of homotypic fusion of synaptic vesicles in vitro. (A,B) Synaptic vesicles prepared from the hs-GAL4/UASRab5N142I mutant flies were electron microscopically observed before (A) and after (B) fusion reaction. Scale bar, 200 nm. (C) The averaged diameters of synaptic vesicles prepared from the wild-type and mutant flies were measured on electron micrographs before (open bars) and after (shaded bars) fusion reaction. (D) Synaptic vesicles prepared from the wild-type and mutant flies were subjected to velocity sedimentation before (0 min) and after (15 min) the fusion reaction, and detected by immunoblotting using anti-synaptotagmin antibodies. (E) Synaptic vesicles from fractions (3+4) and (5+6) of the mutant flies were separately collected and their averaged diameters were measured on the electron micrographs.