importin 13 (Ran-binding protein 13, RanBP13, IPO13, karyopherin 13, Kap13)

Function

• nuclear protein import as nuclear transport receptor
• serves as receptor for nuclear localization signals (NLS) in cargo substrates
• thought to mediate docking of importin/substrate complex to the nuclear pore complex (NPC) through binding to nucleoporin
• 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 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 (putative)
• mediates the nuclear import of UBC9, the RBM8A/MAGOH complex, PAX6 & probably other members of the paired homeobox family
• also mediates nuclear export of eIF-1A
• cytoplasmic release of eIF-1A is triggered by the loading of import substrates onto IPO13
• interacts with UBC9, RBM8A, eIF-1A & PAX6

Structure

• belongs to the importin beta family
• contains 14 HEAT repeats
• contains 1 importin N-terminal domain

Compartment

cytoplasm, nucleus

Expression

• expressed in fetal brain, heart, intestine & kidney

More general terms

• importin beta subunit

Additional terms

• importin complex (NLS-binding protein)
• Ran-binding protein M; Ran-binding protein 9; RanBP9; BPM-L; BPM90; RanBPM; RanBP7 (RANBP9, RANBPM)

Database

• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:9670
• UniProt: http://www.uniprot.org/uniprot/O94829.html