RAB2B belongs to the Rab family of the small GTPase superfamily. Rab proteins are key regulators of intracellular membrane trafficking, acting from the formation of transport vesicles through to their fusion with target membranes. Like other Rabs, RAB2B cycles between an inactive GDP-bound state and an active GTP-bound state. In the active state it drives transport of vesicular carriers from donor organelles to acceptor organelles, regulating the membrane traffic that maintains organelle identity and morphology. Specifically, RAB2B regulates the compacted morphology of the Golgi.

Beyond classical trafficking, RAB2B promotes cytosolic DNA-induced innate immune responses. It regulates interferon responses against DNA viruses through the CGAS-STING signalling axis. Together with RAB2A, it is redundantly required for efficient autophagic flux, so the two paralogues can compensate for one another in this process. UniProt records the protein at the cell membrane, endoplasmic reticulum membrane, Golgi apparatus membrane, the acrosome of secretory vesicles and the autophagosome membrane.

Members of the Rab family are nontransforming, monomeric GTP-binding proteins of the Ras superfamily. They contain four highly conserved regions involved in GTP binding and hydrolysis, which is consistent with the EC 3.6.5.2 classification, and they are prenylated, membrane-bound proteins involved in vesicular fusion and trafficking. The RAB2B gene is classed by HGNC in the group of RAB, member RAS oncogene GTPases, and the mouse ortholog is Rab2b. Researchers studying the RAB2B protein often consider it alongside RAB2A and other Rab GTPases.