Cooper - The Cell fig 8.10
G.M. Cooper fig 8.10
Figure 8.10. Role of the Ran protein in nuclear import.
Transport through the nuclear pore complex is driven by a gradient of Ran/GTP, with a high concentration of Ran/GDP in the cytoplasm and a high concentration of Ran/GTP in the nucleus. Complexes form between target proteins containing nuclear localization signals (NLS), importin-α, and importin-β in the cytoplasm where Ran is in the GDP-bound form. Following transport through the nuclear pore complex, Ran/GTP binds to importin-β, releasing importin-α and the target protein in the nucleus. The Ran/GTP-importin-β complex is then trans-ported back to the cytoplasm, where the Ran GTPase-activating protein (Ran-GAP) stim-ulates hydrolysis of the bound GTP to form Ran/GDP. This conversion of Ran/ GTP to Ran/GDP is accompanied by release of importin-β.