The directionality of transport is maintained by a small monomeric protein Ran, complexed with GTP. Ran-GTP helps nuclear export receptors or exportins to load the cargo, and binds to the import receptor or importin to unload the cargo in the nucleus. Within the nucleus, Ran is regulated by the chromatin-bound Ran-Guanine nucleotide exchange factor or Ran-GEF, which converts RanGDP to RanGTP. In the cytosol, Ran GTPase activating protein or Ran-GAP associates with Ran-binding protein RanBP1 and accelerates the hydrolysis of Ran GTP to Ran GDP. The differential localization of Ran-specific regulators ensures a much higher concentration of Ran-GTP in the nucleus than in the cytosol. During protein import, Ran-GTP binds with the incoming importin-cargo complex, facilitating the cargo release in the nucleus. A higher concentration of the importin-cargo complex in the cytosol further drives cargo import into the nucleus. In contrast, during nuclear export, Ran-GTP increases the cargo binding affinity of exportins inside the nucleus. A higher concentration of exportin-cargo complex in the nucleus compared to the cytosol ensures their unidirectional trafficking.