Endosomal protein that may be involved in endocytosis (PubMed:16103374). Involved in the trafficking of proteins from prevacuolar compartments (PVCs) to vacuoles (PubMed:23682115, PubMed:24824487). May activate the MON1-CCZ1 complex which acts as guanine nucleotide exchange factors (GEF) for Rab7 protein family, and serves as a link between Rab5 and Rab7 families in PVCs, and mediates PVC maturation (PubMed:24824487). Involved in vacuolar transport of storage proteins with EREX as effector. Regulates membrane trafficking to protein storage vacuoles (PSVs) (PubMed:27288222). Regulated by guanine nucleotide exchange factors (GEFs) which promote the exchange of bound GDP for free GTP. Interacts with VPS9A homodimer (PubMed:18055610, PubMed:20833725). Interacts with TCTP1 (PubMed:20736351). Interacts with MON1 (PubMed:24824487). Interacts with EREX (via PX domain) (PubMed:27288222). Binds to VPS3 (PubMed:29463724). Strong co-localization with VPS3 and VPS18 in cytoplasmic puncta. Expressed in roots and actively dividing cells. Expressed during pollen germination and pollen tube growth. Activated by VPS9A. Over-expression of the constitutively active GTP-bound mutant of Leu-69 induces the formation of large ring-like structures of 1-2 micrometers in diameter. Belongs to the small GTPase superfamily. Rab family.