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. Homodimer. Interacts with VAMP2 (synaptobrevin-2), prenylated Rab proteins, GDI1, NRDG1 and PCLO (By similarity). According to some authors, it is an integral membrane protein, while others showed that it is cytoplasmic and membrane-associated to Golgi and synaptic vesicles. Belongs to the PRA1 family.