The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different sets of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (By similarity). The physiological function of RAB42 remains undefined (Probable). . This is the function of RAB42 (RAB42, member RAS oncogene family, Ensembl gene identifier ENSG00000188060).