Rab GTPase family 1 includes the yeast homolog Ypt1
Rab1/Ypt1 subfamily. Rab1 is found in every eukaryote and is a key regulatory component for the transport of vesicles from the ER to the Golgi apparatus. Studies on mutations of Ypt1, the yeast homolog of Rab1, showed that this protein is necessary for the budding of vesicles of the ER as well as for their transport to, and fusion with, the Golgi apparatus. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which facilitate Rab recycling by masking C-terminal lipid binding and promoting cytosolic localization. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.