Functions in nuclear protein import, either in association with an adapter protein, like an importin-alpha subunit, which binds to nuclear localization signals (NLS) in cargo substrates, or by acting as autonomous nuclear transport receptor. Acting autonomously, serves itself as NLS receptor. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex 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 and the three components separate 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 thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. Mediates autonomously the nuclear import of ribosomal proteins RPL23A, RPS7 and RPL5. Binds to a beta-like import receptor binding (BIB) domain of RPL23A. In association with IPO7 mediates the nuclear import of H1 histone. In vitro, mediates nuclear import of H2A, H2B, H3 and H4 histones. In case of HIV-1 infection, binds and mediates the nuclear import of HIV-1 Rev. Imports PRKCI into the nucleus. Forms a complex with an importin alpha subunit. Forms a heterodimer with IPO7. Interacts with IPO7, SNUPN, RPL23A and XPO1. The KPNB1/IPO7 heterodimer interacts with H1 histone. Interacts with H2A, H2B, H3 and H4 histones. Component of an import snRNP complex composed of KPNB1, SNUPN, SMN1 and ZNF259. Component of a nuclear export receptor complex composed of KPNB1, Ran, SNUPN and XPO1. Binds to HIV-1 Rev and Tat. Interacts with HTLV-1 Rex. Interacts with SRY. Interacts with PRKCI/atypical protein kinase C iota. Interacts with human respiratory syncytial virus (HRSV) protein M. Interacts with KPNA7. Belongs to the importin beta family. Note: This description may include information from UniProtKB.
Molecular Function: protein domain specific binding; protein binding; enzyme binding; zinc ion binding; nuclear localization sequence binding; Ran GTPase binding; protein transporter activity
Biological Process: ribosomal protein import into nucleus; viral reproduction; protein import into nucleus, translocation; apoptosis; protein import into nucleus; cytokine and chemokine mediated signaling pathway; NLS-bearing substrate import into nucleus; DNA fragmentation during apoptosis; viral infectious cycle; cell structure disassembly during apoptosis
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.