RanBP2 (also called E3 SUMO-protein ligase RanBP2, 358 kDa nucleoporin, and nuclear pore complex (NPC) protein Nup358) is a giant nucleoporin that localizes to the cytosolic face of the NPC. RanBP2 contains a leucine-rich region, 8 zinc-finger motifs, a cyclophilin A homologous domain, and 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. All eukaryotic cells contain RanBP1, but in vertebrates however, the main RanBP seems to be RanBP2. There is no RanBP2 ortholog in yeast. Transport complex disassembly is accomplished by a small ubiquitin-related modifier-1 (SUMO-1)-modified version of RanGAP that is bound to RanBP2. RanBP1 acts as a second line of defense against exported RanGTP#importin complexes which have escaped from dissociation by RanBP2. RanBP2 also interacts with the importin subunit beta-1. RabBD shares structural similarity to the PH domain, but lacks detectable sequence similarity. The first RanBD2 is present in this hierarchy.
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