RAB21, Member RAS Oncogene Family (RAB21)

RAB21 belongs to the RAB family of small GTP-binding proteins that regulate intracellular vesicle targeting . The deduced 225-amino acid RAB21 protein has a calculated molecular mass of 24.5 kD. Like other RAB proteins, RAB21 contains 6 GTP-binding domains and C-terminal cysteines required for prenylation. Northern blot analysis detected transcripts of 1.8, 2.5, and 4.0 kb in lung, kidney, liver, esophagus, stomach, jejunum, rectum, and all human cell lines examined. Immunofluorescence analysis showed RAB21 associated with the endoplasmic reticulum in nonpolarized Caco2 cells and with apical membranes and late endosomes or lysosomes in differentiated, polarized Caco2 cells. RAB21 was also detected in capillary endothelial cells and in some cells of the lamina propria.