Involved in the transport of proteins between the endosomes and the trans-Golgi network (PubMed:8440258). Involved in the recruitment of SGSM2 to melanosomes and is required for the proper trafficking of melanogenic enzymes TYR, TYRP1 and DCT/TYRP2 to melanosomes in melanocytes (By similarity). Interacts (preferentially in its GTP-bound form) with GCC2 (via its GRIP domain) (PubMed:16885419). Interacts (GTP-bound form) with SGSM1; the GDP-bound form has much lower affinity for SGSM1. Interacts with SGSM2. The GTP-bound form but not the GDP-bound form interacts with HPS4 and the BLOC-3 complex (heterodimer of HPS1 and HPS4) but does not interact with HPS1 alone (By similarity). Colocalizes with OSBPL1A at the late endosome. Recruited to phagosomes containing S.aureus or M.tuberculosis. Belongs to the small GTPase superfamily. Rab family.