RAB GTPase Binding Effector Protein 1 (RABEP1)

The small GTPase RAB5 is a rate-limiting component in membrane docking or fusion in the early endocytic pathway. The GTP-bound form of RAB5 is the active conformation. Using a yeast 2-hybrid screen, Stenmark et al. (1995) identified HeLa cell cDNAs encoding a protein that interacted with the GTP-bound form of RAB5. The predicted 862-amino acid protein was designated rabaptin-5, a name combining the Greek word 'apto,' meaning 'touch', with RAB5. Both the N- and C-terminal regions of rabaptin-5 are predicted to be mainly alpha-helical and contain heptad repeats characteristic of coiled-coil domains. Western blot analysis of mammalian cell extracts indicated that the 115-kD protein is ubiquitously expressed and is present in a major cytosolic and minor endosome-bound pool.