Sandbox Reserved 709: Difference between revisions
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Once the import complex enters the nucleus, it must be dissociated to release the cargo protein. Then, importin α must be recycled to the cytoplasm. | Once the import complex enters the nucleus, it must be dissociated to release the cargo protein. Then, importin α must be recycled to the cytoplasm. | ||
* '''Step 4 :''' Cargo release is driven by '''Ran''', a G-protein that is found in Ran-GTP form in the nucleus due to a higher rate of RanGEF than RanGAP in chromatin. It binds to importin β, causing an important change in shape and reducing importin β affinity for importin α IBB. | * '''Step 4 :''' Cargo release is driven by '''[[Ran|Ran]]''', a G-protein that is found in Ran-GTP form in the nucleus due to a higher rate of RanGEF than RanGAP in chromatin. It binds to importin β, causing an important change in shape and reducing importin β affinity for importin α IBB. | ||
* '''Step 5 :''' Importin β can pass through the NPC thanks to Ran-GTP. A Ran-BP (''Ran-Binding Protein'') is a major component of the NPC’s cytoplasmic filaments. Thus, Ran-GTP is not released in the cytoplasm, but is still bound with importin β to the NPC. Ran-BP is also able to bind to a RanGAP. Finally, RanGAP locally promotes hydrolysis of Ran-GTP into Ran-GDP, leading to its own release, and importin β release by the same. | * '''Step 5 :''' Importin β can pass through the NPC thanks to Ran-GTP. A Ran-BP (''Ran-Binding Protein'') is a major component of the NPC’s cytoplasmic filaments. Thus, Ran-GTP is not released in the cytoplasm, but is still bound with importin β to the NPC. Ran-BP is also able to bind to a RanGAP. Finally, RanGAP locally promotes hydrolysis of Ran-GTP into Ran-GDP, leading to its own release, and importin β release by the same. | ||
* '''Step 6 :''' '''Nup50''' (also called '''Npap60'''), a nucleoplasmin, weakens the link between importin α and the NLS of the cargo. Thus the cargo protein is now free in the nucleoplasm. | * '''Step 6 :''' '''Nup50''' (also called '''Npap60'''), a nucleoplasmin, weakens the link between importin α and the NLS of the cargo. Thus the cargo protein is now free in the nucleoplasm. | ||
