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 GDI. Homodimer. Interacts with VAMP2 (synaptobrevin-2), GDI1, and PCLO (By similarity). Interacts specifically with prenylated Rab proteins; strongly with RAB4B, RAB5A and RAB5C, and weakly with RAB4A, RAB6, RAB7A, RAB17 and RAB22. Interacts with NDRG1. 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. Ubiquitous. Strongest expression found in placenta, pituitary gland, kidney, lung and stomach. In fetal tissues, it is more abundant in kidney and lung. Belongs to the PRA1 family. In contrast to the mouse ortholog, it does not interact with Ras.