Importin

Function Importins (IPO) mediate the import of cellular proteins into the nucleus by binding to the Nuclear Localization Signal (NLS). IPO has 2 subunits: α and β. IPO-α is an adaptor protein which binds the NLS. IPOs can contain one or two NLS motifs. IPO-α contains several armadillo repeats with two NLS-binding sites and an IPO-β binding (IBB) site. IPO-β contains 19 HEAT (solenoid domain) repeats. Many nuclear proteins contain Phe-Gly sequences which can bind to HEAT repeats and thus be transported. See also Protein Transport Membrane Protein. Disease IPO-α isoform expression is altered in many kinds of cancer. Relevance Specific IPO-α isoforms are critical in nerve regenerative response after injury. Loss of IPO-α expression in aging myocardial cells could make recovery after heart disease in elderly patients more difficult.

spinqualitylabelsall models Structure of yeast importin α NLS-binding domain (grey) complex with nucleoplasmin peptide (green) (PDB code 1ee5). Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

3D structures of importin3D structures of importin

Updated on 15-June-2017

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• IPO-α
  • 1ial – mIPO NLS-binding domain – mouse
    
  • 1bk5 – yIPO NLS-binding domain - yeast
    
  • 4tnm – IPO armadillo repeat domain – Arabidopsis thaliana
    
• IPO-α complex with NLS peptide
  • 1ejl – mIPO NLS-binding domain + SV40 large T antigen
    
  • 1ejy – mIPO NLS-binding domain + nucleoplasmin
    
  • 2ynr – mIPO NLS-binding domain + B54NLS
    
  • 2yns – rIPO NLS-binding domain + B54NLS - rice
    
  • 1bk6 – yIPO NLS-binding domain + SV40 large T antigen
    
  • 1ee4 – yIPO NLS-binding domain (mutant) + c-Myc
    
  • 1ee5 – yIPO NLS-binding domain (mutant) + nucleoplasmin
    
  • 1un0, 2c1t – yIPO NLS-binding domain (mutant) + Nup2
    
  • 5h2x, 5h2w – yIPO NLS-binding domain + ubiquitin-like specific protease
    
  • 4xzr – yIPO NLS-binding domain + HEH1
    
  • 4pvz – yIPO NLS-binding domain + HEH2
    
  • 4rxh – IPO NLS-binding domain + SV40 large T antigen – Neurospora crassa
    
• IPO-α complex with protein
  • 1wa5 – yIPO NLS-binding domain + GTPase Ran + IPO-α re-exporter
    
• IPO-α 1
  • 3wpt – hIPO NLS-binding domain - human
    
  • 4b8j – rIPO
    
• IPO-α 1 complex with NLS peptide
  • 4mz5, 4mz6 – mIPO NLS-binding domain + dUTPase
    
  • 4oih – mIPO NLS-binding domain + guanine nucleotide exchange factor SRM1
    
  • 5svz – mIPO NLS-binding domain + TAT NLS motif
    
  • 5wum, 5wun, 5x8n – mIPO NLS-binding domain + Epstein Barr antigen
    
  • 5huw – mIPO NLS-binding domain + HSVI large terminase
    
  • 5huy – mIPO NLS-binding domain + HSMV small terminase
    
  • 5hhg, 5fc8 – mIPO NLS-binding domain + dengue 2 NS5
    
  • 5ekg, 5ekf, 5e6q – mIPO NLS-binding domain + XPG2
    
  • 5d5k – mIPO NLS-binding domain + PARP 2
    
  • 5ctt – mIPO NLS-binding domain + SART3/TIP110
    
  • 5b56 – mIPO NLS-binding domain + HIV-1 VPR
    
  • 4zdu – mIPO NLS-binding domain + influenza nucleoprotein
    
  • 4yi0 – mIPO NLS-binding domain + Nup121
    
  • 5klr, 5klt – mIPO NLS-binding domain + NLS
    
  • 5k9s – mIPO NLS-binding domain + HNF-b
    
  • 4b18 – hIPO NLS-binding domain + telomerase reverse transcriptase
    
  • 4wv6 – hIPO NLS-binding domain + TFIID
    
  • 4b8o – rIPO NLS-binding domain + SV40
    
  • 4b8p – rIPO NLS-binding domain + A89
    
  • 4bpl – rIPO NLS-binding domain + nucleoplasmin
    
  • 4bqk – rIPO NLS-binding domain + VirD2
    
• IPO-α 1 complex with protein
  • 2jdq – hIPO NLS-binding domain + polymerase basic protein 2 C terminal
    
  • 3tj3 – hIPO NLS-binding domain + Nup50 N terminal
    
  • 2jdq – hIPO NLS-binding domain + telomerase reverse transcriptase peptide
    
  • 4uaf – mIPO NLS-binding domain + influenza RNA polymerase
    
• IPO-α 2
  • 3tpo – mIPO
    
  • 1iq1 – mIPO NLS-binding + autoinhibitory peptide domains
    
  • 4e4v – hIPO NLS-binding domain (mutant)
    
• IPO-α 2 complex with NLS peptide
  • 1pjm – mIPO NLS-binding domain + retinoblastoma-associated protein
    
  • 1pjn – mIPO NLS-binding domain + histone-binding protein N1/N2
    
  • 1q1s, 1q1t – mIPO NLS-binding domain + SV40 large T antigen
    
  • 1y2a, 3q5u – mIPO NLS-binding domain + phospholipid scramblase
    
  • 2c1m – mIPO NLS-binding domain + Nup50
    
  • 3btr – mIPO NLS-binding domain + androgen receptor
    
  • 3knd – mIPO NLS-binding domain + targeting protein for KXLP2
    
  • 3l3q – mIPO NLS-binding domain + library peptide
    
  • 3oqs – mIPO NLS-binding domain + CLIC4
    
  • 3rz9 – mIPO NLS-binding domain + KU80
    
  • 3rzx – mIPO NLS-binding domain + KU70
    
  • 3tpm – mIPO NLS-binding domain + MAL
    
  • 3ve6 – mIPO NLS-binding domain + Venezuelan equine encephalitis virus
    
  • 3uvu – mIPO NLS-binding domain + flap endonuclease
    
  • 3ukw, 3ukx – mIPO NLS-binding domain + BIMAX
    
  • 3uky, 3ukz, 3ul0 – mIPO NLS-binding domain + nuclear CAP-binding protein
    
  • 3ul1 – mIPO NLS-binding domain + nucleoplasmin
    
  • 4htv – mIPO NLS-binding domain + capsid protein
    
  • 4ba3 – mIPO NLS-binding domain + A89NLS
    
  • 3zio, 3zip, 3ziq, 3zir – mIPO NLS-binding domain + minor site-specific NLS
    
  • 3zin – mIPO NLS-binding domain + nucleolar RNA helicase
    
• IPO-α 2 complex with protein
  • 3fex, 3fey – mIPO NLS-binding domain + nuclear CAP-binding protein
    
• IPO-α 3
  • 4uae – hIPO NLS-binding domain + influenza RNA polymerase
    
• IPO-α 6
  • 4u2x – hIPO C terminal + ebola VP24
    
• IPO-α 7
  • 4uad – hIPO NLS-binding domain + influenza RNA polymerase
    
• IPO-β
  • 4xrk – IPO – Chaetomium thermophilum
    
• IPO-β 1 (karyopherin β 1)
  • 3nd2 – yIPO
    
  • 1gcj – mIPO N terminal
    
• IPO-β 1 complex with protein
  • 1qgx, 1qgr – hIPO + IPO-α 2 IBB domain
    
  • 1ibr – hIPO + GTPase Ran
    
  • 2bku, 3ea5 – yIPO + GTPase Ran
    
  • 1f59, 1o6p, 1o6o – hIPO + FXFG nucleoporin repeats
    
  • 1m5n – hIPO HEAT repeats 1-11 + parathyroid hormone-related protein NLS peptide
    
  • 2p8q, 2q5d, 2qna, 3lww – hIPO + RNA U transporter N terminal
    
  • 1qgr, 3w5k – hIPO + zinc finger protein SNAI1
    
  • 2bpt – yIPO + Nup1
    
  • 1ukl – mIPO + SREBP-2
    
• IPO-β 2 (Transportin 1)
  • 2z5j, 2qmr – hIPO
    
• IPO-β 2 complex with protein
  • 2h4m, 2ot8, 2z5n – hIPO + hnRNP peptide
    
  • 2z5k, 2z5m – hIPO + nuclear RNA export factor peptide
    
  • 2z5o – hIPO + JKTBP peptide
    
  • 4fdd, 4jlq, 4oo6 – hIPO + RNA binding protein peptide
    
  • 4fq3 – hIPO + FUS peptide
    
  • 5tqc – hIPO + RPL4 peptide
    
  • 5j3v – hIPO + histone H3 peptide
    
• IPO-β 3 (Karyopherin β 3)
  • 3w3t – yIPO
    
  • 3w3u, 3w3v – yIPO (mutant)
    
  • 3w3w – yIPO + STE12P
    
  • 3w3x – yIPO + PHO4
    
  • 3w3y – yIPO + Nup53P
    
  • 3w3z – yIPO + RANGTP
    
  • 5h2v – yIPO + ubiquitin-like specific protease
    
  • 4zj7 – yIPO + CDC14
    
• IPO-12 (Transportin-3)
  • 4c0p – hIPO
    
  • 4c0o – hIPO + serine/arginine-rich splicing factor
    
  • 4c0q, 4ol0 – hIPO + GTPase Ran
    
• IPO-13 (karyopherin 13)
  • 2x19 – hIPO + GTPase Ran
    
  • 2xwu – hIPO + UBC9
    
  • 3zjy – hIPO + GTPase Ran + EIF-1A