KPNB1 Protein, Human (His)

KPNB1 functions prominently in nuclear protein import, operating either in collaboration with an adapter protein, such as an importin-alpha subunit, which recognizes nuclear localization signals (NLS) in cargo substrates, or autonomously as a nuclear transport receptor. In autonomous mode, it serves as its own NLS receptor. The importin/substrate complex docks to the nuclear pore complex (NPC) through KPNB1, binding to nucleoporin FxFG repeats, and is subsequently translocated through the pore by an energy-requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta, leading to the separation of the components, and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm, where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is presumed to be influenced by the asymmetric distribution of GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. KPNB1 autonomously mediates the nuclear import of ribosomal proteins RPL23A, RPS7, and RPL5. Additionally, it collaborates with IPO7 to mediate the nuclear import of H1 histone, and in vitro, facilitates the nuclear import of H2A, H2B, H3, and H4 histones. In the context of HIV-1 infection, it binds and mediates the nuclear import of HIV-1 Rev. Moreover, KPNB1 imports various proteins into the nucleus, including SNAI1, PRKCI, and forms complexes with importin alpha subunits. It interacts with a range of proteins such as XPO1, SNUPN, H2A, H2B, H3, H4 histones, SRY, PRKCI, KPNA2, KPNA7, SNAI1, SNAI2, SLC35G1, STIM1, DCAF8, RAN, NUMA1, ZBED1/hDREF, SRP19, RPL23A, RPS7, RPL5, and PARP16.