ID:IMA4_HUMAN DESCRIPTION: RecName: Full=Importin subunit alpha-4; AltName: Full=Importin alpha Q1; Short=Qip1; AltName: Full=Karyopherin subunit alpha-4; FUNCTION: Functions in nuclear protein import as an adapter protein for nuclear receptor KPNB1. Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. 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. In vitro, mediates the nuclear import of human cytomegalovirus UL84 by recognizing a non- classical NLS. In vitro, mediates the nuclear import of human cytomegalovirus UL84 by recognizing a nonclassical NLS. SUBUNIT: Forms a complex with importin subunit beta-1. SUBCELLULAR LOCATION: Cytoplasm (By similarity). Nucleus (By similarity). TISSUE SPECIFICITY: Highly expressed in testis, ovary, small intestine, heart, skeletal muscle, lung and pancreas, but barely detectable in kidney, thymus, colon and peripheral blood leukocytes. DOMAIN: Consists of an N-terminal hydrophilic region, a hydrophobic central region composed of 10 repeats, and a short hydrophilic C-terminus. The N-terminal hydrophilic region contains the importin beta binding domain (IBB domain), which is sufficient for binding importin beta and essential for nuclear protein import. DOMAIN: The IBB domain is thought to act as an intrasteric autoregulatory sequence by interacting with the internal autoinhibitory NLS. Binding of KPNB1 probably overlaps the internal NLS and contributes to a high affinity for cytoplasmic NLS-containing cargo substrates. After dissociation of the importin/substrate complex in the nucleus the internal autohibitory NLS contributes to a low affinity for nuclear NLS- containing proteins (By similarity). DOMAIN: The major and minor NLS binding sites are mainly involved in recognition of simple or bipartite NLS motifs. Structurally located within in a helical surface groove they contain several conserved Trp and Asn residues of the corresponding third helices (H3) of ARM repeats which mainly contribute to binding (By similarity). SIMILARITY: Belongs to the importin alpha family. SIMILARITY: Contains 10 ARM repeats. SIMILARITY: Contains 1 IBB domain. CAUTION: Was termed (PubMed:9395085) importin alpha-3.
The RNAfold program from the Vienna RNA Package is used to perform the secondary structure predictions and folding calculations. The estimated folding energy is in kcal/mol. The more negative the energy, the more secondary structure the RNA is likely to have.
ModBase Predicted Comparative 3D Structure on O00629
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Orthologous Genes in Other Species
Orthologies between human, mouse, and rat are computed by taking the best BLASTP hit, and filtering out non-syntenic hits. For more distant species reciprocal-best BLASTP hits are used. Note that the absence of an ortholog in the table below may reflect incomplete annotations in the other species rather than a true absence of the orthologous gene.
Gene Ontology (GO) Annotations with Structured Vocabulary
Molecular Function: GO:0005515 protein binding GO:0008139 nuclear localization sequence binding GO:0008565 protein transporter activity GO:0061608 nuclear import signal receptor activity
Biological Process: GO:0006606 protein import into nucleus GO:0006607 NLS-bearing protein import into nucleus GO:0015031 protein transport GO:0016032 viral process GO:0019054 modulation by virus of host process GO:0042542 response to hydrogen peroxide
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Sequence and Links to Tools and Databases 
Common Gene Haplotype Alleles 
