General Rab protein regulator required for vesicle formation from the Golgi complex. May control vesicle docking and fusion by mediating the action of Rab GTPases to the SNARE complexes. In addition it inhibits the removal of Rab GTPases from the membrane by GDI1 (By similarity). Homodimer. Interacts with VAMP2 (synaptobrevin-2), GDI1, NRDG1 and PCLO (By similarity). Interacts with prenylated Rab proteins (including RAB5 and RAB6), and with the members of the Ras superfamily HRAS, RHOA, TC21, and RAP1A. According to PubMed:11535589, it is an integral membrane protein, while other authors showed that it is cytoplasmic and membrane-associated to Golgi and synaptic vesicles. Belongs to the PRA1 family. Interaction with the Ras-like GTPases failed to be confirmed in other species.