Figure 9.

Motility is potently inhibited by GTPγS or AlF₄⁻. Motility assays were performed using samples containing no additives (Control), 1 μM GTPγS ± 100 μM GTP, AlF₄⁻ (20 μM AlCl₃ + 3 mM NaF), 20 μM AlCl₃, or 3 mM NaF. After 60–90 min, the extent of membrane tubule formation was measured as decribed in MATERIALS AND METHODS. Each experimental condition was compared with a control in a minimum of three separate experiments. We consistently observed that membrane tubule formation was nearly abolished by GTPγS or AlF₄⁻, that the effects of GTPγS were minimized by addition of a 100-fold molar excess of GTP, and that neither AlCl₃ nor NaF alone was inhibitory. Illustrated here are merged results from two representative experiments, one of which examined GTPγS ± GTP and the other of which tested AlF₄⁻, AlCl₃, and NaF. GTPγS and AlF₄⁻ also nearly abolished motility of small Golgi fragments at early stages of the experiment, but neither agent prevented formation of membrane aggregates.