FIG. 8.
Model of Xpo-t translocation and recycling through the NPC. Xpo-t binds to RanGTP in the nucleus (step 1), and the export complex then binds to Nup153 (via the N terminus of Xpo-t) at the nuclear side of the NPC (step 2). The complex translocates and binds to RanBP2/Nup358 on the cytoplasmic side of the NPC (step 3), where RanGAP and RanBP1 can stimulate nucleotide hydrolysis on Ran, and Xpo-t is released. The C terminus of Xpo-t can then interact with CAN/Nup214 to position the receptor for efficient import (step 4). The import complex of NTF2/RanGDP may compete Xpo-t from CAN, and both complexes translocate into the nucleoplasm (step 5), where RanGTP can be generated and Xpo-t export complexes can form for another round of translocation.