RAB3C belongs to the small GTPase superfamily and the Rab family. Rab proteins are key regulators of intracellular membrane trafficking, acting at stages from the formation of transport vesicles to their fusion with membranes. Like other Rabs, RAB3C cycles between an inactive GDP-bound form and an active GTP-bound form. The GTP-bound state recruits different sets of downstream effectors to membranes, and these effectors are directly responsible for vesicle formation, movement, tethering and fusion.

The RAB3C gene encodes a small GTPase and is classed by HGNC in the group of RAB, member RAS oncogene GTPases. Its protein product, Ras-related protein Rab-3C, is annotated in UniProt as localising to the cell membrane. As a GTPase it carries the hydrolase activity described by EC 3.6.5.2. The mouse and rat orthologs are both named Rab3c. Two transcript variants encoding different isoforms have been reported for this gene.

According to the NCBI Gene summary, similar small GTPases are involved in vesicle trafficking, and the encoded protein has been shown to play a role in recycling phagocytosed MHC class 1 complexes to the cell surface. This links RAB3C to the trafficking routes that return internalised membrane proteins to the plasma membrane. Researchers studying RAB3C often work alongside other Rab family members, which share the GDP/GTP cycle but direct distinct trafficking steps.