importin beta-3 subunit; karyopherin beta-3 subunit; Ran-binding protein 5 (RANBP5, KPNB3, IPO5)

Function

• nuclear protein import as nuclear transport receptor
• receptor for nuclear localization signals (NLS) in cargo substrates
• thought to mediate docking of importin/substrate complex to the nuclear pore complex through binding to nucleoporin
• the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism
• at the nucleoplasmic side of the nuclear pore complex, Ran binds to the importin, the importin/substrate complex dissociates & importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran
• directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- & GDP-bound forms of Ran between the cytoplasm & nucleus
• mediates nuclear import of ribosomal proteins RPL23A, RPS7 & RPL5
• binds to a beta-like import receptor binding (BIB) domain of RPL23A
• in vitro, mediates nuclear import of H2A, H2B, H3 & H4 histones
• binds RPL23A, RPS7 & RPL5
• interacts with H2A, H2B, H3 & H4 histones

Structure

• belongs to the importin beta family
• contains 6 HEAT repeats
• contains 1 importin N-terminal domain

Compartment

• cytoplasm, nucleus, nucleolus, nuclear rim
• found particularly in the nuclear rim & nucleolus

Pathology

• in case of HIV-1 infection, binds & mediates nuclear import of HIV-1 Rev

More general terms

• importin beta subunit

Additional terms

• importin complex (NLS-binding protein)

Database

• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:3843
• OMIM: https://mirror.omim.org/entry/602008
• UniProt: http://www.uniprot.org/uniprot/O00410.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=3843