RAB18, Member RAS Oncogene Family (RAB18)

Rab proteins are members of a family of Ras-related small GTPases that regulate membrane trafficking in organelles and transport vesicles. The deduced 206-amino acid protein shares 98%, 92%, and 85% identity with the mouse, snail, and worm sequences, respectively. RAB18 contains totally conserved phosphate/Mg(2+)-binding motifs and guanine-binding motifs as well as somewhat variable organelle-targeting regions. Northern blot analysis detected 2.5- and 1.0-kb transcripts in endothelial cells but not in smooth muscle cells or leukocytes. RT-PCR analysis suggested ubiquitous expression, which HPLC analysis determined to be strongest in heart, kidney, pancreas, lung, and liver, with weak expression in brain, placenta, and skeletal muscle.