Ran is Ras-related nuclear protein or GTP-binding nuclear protein. It is a small protein that is involved in transport of large molecules in and out of the cell nucleus. Ran can exist in two states, either bound to GDP or bound to GTP. When bound to GTP, it is capable of binding karyopherins; the transport channels importins and exportins of the nuclear membrane. The proteins importins bind molecules to be transported into the nucleus. These molecules have nuclear localization signals exposed on them. Importin- binds to NLS sequence, which then binds to importin-. The complex thus formed passes through the nuclear pore. Inside the nucleus, RanGTP binds to importin- and displaced it. Another protein called CAS which is an exportin binds RanGTP and displaces importin-, releasing the macromolecules. The importin-RanGTP and importin – CAS-RanGTP complexes diffuse back to cytoplasm. The GTP is hydrolyzed to GDP, which causes the release of importin- and importin- which participates in another cycle of import around. Solution Ran is Ras-related nuclear protein or GTP-binding nuclear protein. It is a small protein that is involved in transport of large molecules in and out of the cell nucleus. Ran can exist in two states, either bound to GDP or bound to GTP. When bound to GTP, it is capable of binding karyopherins; the transport channels importins and exportins of the nuclear membrane. The proteins importins bind molecules to be transported into the nucleus. These molecules have nuclear localization signals exposed on them. Importin- binds to NLS sequence, which then binds to importin-. The complex thus formed passes through the nuclear pore. Inside the nucleus, RanGTP binds to importin- and displaced it. Another protein called CAS which is an exportin binds RanGTP and displaces importin-, releasing the macromolecules. The importin-RanGTP and importin – CAS-RanGTP complexes diffuse back to cytoplasm. The GTP is hydrolyzed to GDP, which causes the release of importin- and importin- which participates in another cycle of import around..