RanBP1 interacts specifically with GTP-charged Ran. RanBP1 does not activate GTPase activity of Ran, but does markedly increase GTP hydrolysis by the RanGTPase-activating protein (RanGAP1). In both mammalian cells and in yeast, RanBP1 acts as a negative regulator of Regulator of chromosome condensation 1 (RCC1) by inhibiting RCC1-stimulated guanine nucleotide release from Ran. In addition to Ran, RanBP1 has been shown to interact with Exportin-1 and Importin subunit beta-1 which docks the NPC at the cytoplasmic side of the nuclear pore complex. RabBP1 contains a single RanBD. The RanBD is present in RanBD1, RanBD2, RanBD3, Nuc2, and Nuc50. Most of these proteins have a single RanBD, with the exception of RanBD2 which has 4 RanBDs. Ran is a Ras-like nuclear small GTPase, which regulates receptor-mediated transport between the nucleus and the cytoplasm. RanGTP hydrolysis is stimulated by RanGAP together with the Ran-binding domain containing acessory proteins RanBP1 and RanBP2. These accessory proteins stabilize the active GTP-bound form of Ran. The Ran-binding domain is found in multiple copies in Nuclear pore complex proteins. RabBD shares structural similarity to the PH domain, but lacks detectable sequence similarity.
Jiyao W et al.(2023). "The conserved domain database in 2023.",