Localization of the importin-{beta} gene to mouse chromosome 11D and rat chromosome 10q32.1
- National Inst. of Radiological Sciences, Chiba (Japan)
- Radiation Effects Research Foundation, Nagasaki (Japan); and others
Importin has been identified as among the cytosolic proteins forming the nuclear pore targeting complex of the nuclear localization sequence-mediated (NLS-mediated) nuclear protein import machinery. The selective import of proteins into the cell nucleus occurs in two steps, both of which require the presence of an NLS. The first step is binding to the cytoplasmic surface of the nuclear pore complex (NPC), which forms channels for diffusion and active transport across the double membrane bilayer of the nuclear envelope. This step requires NLS and soluble factors, namely importin-{alpha} (M{sub r} 60 kDa), importin-{beta} (M{sub r} 90 kDa), and Ran/TC4. The complex consisting of importin-{alpha}, by which the NLS of nuclear proteins is primarily recognized, and importin-{beta} binds the import substrate in the cytosol, which binds to the NPC. This step does not require energy. The second step is the energy-dependent translocation through the NPC. The Ran/TC4 molecule mediates the energy-dependent process. Then, finally, the import substrates and importin-{alpha} are transported into the nucleus. In contrast, importin-{beta} accumulates at the nuclear envelope, but not in the nucleoplasm. In detailed analyses, it was revealed that the binding of the nuclear pore targeting complex to NPC is mediated by importin-{beta}.
- OSTI ID:
- 484350
- Journal Information:
- Genomics, Vol. 36, Issue 1; Other Information: PBD: 15 Aug 1996
- Country of Publication:
- United States
- Language:
- English
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