RAB13, Member RAS Oncogene Family (RAB13)

The predicted 203-amino acid protein has the typical structural features of Ras-related proteins, including a conserved GTP-binding site. RAB13 displays 61% and 56% amino acid identity with the human RAB8 and yeast Sec4 proteins, respectively. These proteins share a long conserved N-terminal region but have divergent C-terminal portions. Northern blot analysis showed that RAB13 is expressed as a 1.2-kb transcript in Caco-2 cells. Immunoblot analysis using antibodies against RAB13 detected a 24-kD protein in Caco-2 cell lysates. Immunofluorescence studies demonstrated that RAB13 colocalizes with the tight junction marker ZO1 (TJP1) in epithelial cells. In cells devoid of tight junctions, RAB13 associates with vesicles dispersed throughout the cytoplasm.