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importin beta-2 subunit (karyopherin beta-2 subunit, KPNB2, transportin-1, M9 region interaction protein, MIP, TNPO1, MIP1, TRN)
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
- involved in nuclear import of M9-containing proteins
- in vitro, binds directly to the M9 region of the heterogeneous nuclear ribonucleoproteins (hnRNP), hnRNPA1 & hnRNPA2 & mediates their nuclear import
- appears also to be involved in hnRNPA1 & hnRNPA2 nuclear export
- 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, & SRP19
- binds HNRPA1, HNRPA2, HNRPDL, RPL23A, RPS7, RPL5, RAN & SRP19
Structure:
- belongs to the importin beta family
- contains 8 HEAT repeats
- contains 1 importin N-terminal domain
Compartment: cytoplasm. nucleus
Pathology:
- in case of HIV-1 infection, binds & mediates the nuclear import of HIV-1 Rev
Related
importin complex (NLS-binding protein)
General
importin beta subunit
transportin (TNPO)
Properties
SIZE: entity length = 890 aa
MW = 101 kD
COMPARTMENT: cytoplasm
cell nucleus
MOTIF: Importin N-terminal {33-101}
HEAT repeat {124-161}
HEAT repeat {170-207}
HEAT repeat {211-248}
acidic region {350-368}
MOTIF: acidic residue (SEVERAL)
HEAT repeat {393-430}
HEAT repeat {434-471}
HEAT repeat {476-513}
HEAT repeat {560-599}
HEAT repeat {663-700}
Database Correlations
OMIM 602901
UniProt Q92973
Entrez Gene 3842
References
- UniProt :accession Q92973