Removal of Rab GTP-binding proteins from Golgi membranes by GDP dissociation inhibitor inhibits inter-cisternal transport in the Golgi stacks.

Rab proteins are a family of Ras-like GTPases involved in intracellular membrane traffic. Rab GDI, a cytosolic protein which inhibits the dissociation of GDP from various Rab proteins, is required to maintain a pool of Rab proteins in the cytosol. We describe the purification of a cytosolic factor from bovine liver that inhibits intra-cisternal transport between the Golgi stacks. We identify this factor as a Rab GDI. Half-maximal inhibition of transport was observed in the presence of the same concentration of GDI that is required for removal of Rab proteins from the Golgi.