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. GTP + H2O = GDP + H(+) + phosphate Interacts with KCNMA1 (PubMed:22935415). 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 (GDP-bound form) with ZFYVE27 (By similarity). Interacts (GDP-bound form) with KIF5A in a ZFYVE27-dependent manner (By similarity). Interacts with RELCH (PubMed:29514919). Interacts (in GTP-bound form) with TBC1D8B (via domain Rab-GAP TBC) (By similarity). Abundantly expressed in brain, heart and testis. Also detected in kidney and pancreatic islets. Citrullinated by PADI4. Belongs to the small GTPase superfamily. Rab family.