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 set of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion. The small Rab GTPase RAB11B plays a role in endocytic recycling, regulating apical recycling of several transmembrane proteins including cystic fibrosis transmembrane conductance regulator/CFTR, epithelial sodium channel/ENaC, potassium voltage-gated channel, and voltage-dependent L-type calcium channel. May also regulate constitutive and regulated secretion, like insulin granule exocytosis. Required for melanosome transport and release from melanocytes. Also regulates V-ATPase intracellular transport in response to extracellular acidosis (By similarity). GTP + H2O = GDP + H(+) + phosphate Interacts with KCNMA1 (By similarity). Interacts with RAB11FIP1, RAB11FIP2, RAB11FIP3 and RAB11FIP4 (By similarity). May interact with TBC1D14 (By similarity). Interacts with ATP6V1E1 (By similarity). Interacts with PI4KB (By similarity). Interacts with RELCH (By similarity). Interacts (in GTP-bound form) with TBC1D8B (via domain Rab-GAP TBC) (By similarity). Citrullinated by PADI4. Belongs to the small GTPase superfamily. Rab family.