Protein transport. Probably involved in vesicular traffic (By similarity). Specifically binds guanine nucleotides. Via its C-terminal end interacts with the Rab GDP dissociation inhibitor (RabGDI). Interacts with YIF1, YIP3, YIP4 and YIP5. Present with 1360 molecules/cell in log phase SD medium. Belongs to the small GTPase superfamily. Rab family.