Fig. 8. Effects of guanosine nucleotide analogues on MT-based motility and fission of early endocytic vesicles. MT-bound vesicles were incubated for 5 minutes with buffer alone (control) or with buffer containing 4 mM GTP--S, GDP--S, GDP, GDP plus 0.5 µM Rab-GDI, or 2 µM GST-Rab4 as indicated. Guanine nucleotides were exchanged into GST-Rab4 by preincubation immediately before addition to vesicles. ATP (50 µM) was added to produce vesicle motility, and this activity was scored. The bars in panel A indicate the percentage of MT-bound vesicles that moved upon ATP addition. For each experiment, the number of motile vesicles versus the total number of MT-bound vesicles that were examined is in parentheses. The bars in panel B indicate the percentage of moving vesicles that underwent fission. For each experiment, the number of vesicles that underwent fission versus the number of motile vesicles is in parentheses. *P<0.001 versus control.