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. Proteins can contain one or two NLS motifs. IPO-α contains several armadillo repeats with two NLS-binding sites and an IPO-β binding site (IBB). IPO-β contains 19 HEAT repeats. Many nuclear proteins contain Phe-Gly sequences which can bind to HEAT repeats and thus be transported.

Disease

Relevance

Structural highlights

3D structures of importin

Updated on 17-June-2014

IPO-α

1ial – mIPO residues 44-496 – mouse

1bk5 – yIPO NLS-binding domain - yeast

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
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

IPO-α complex with protein

1wa5 – yIPO NLS-binding domain + GTPase Ran + IPO-α re-exporter

IPO-α 1

IPO-α 1 complex with NLS peptide

4mz5, 4mz6 – mIPO NLS-binding domain + dUTPase

4oih – mIPO NLS-binding domain + guanine nucleotide exchange factor SRM1

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

IPO-α 2

3tpo – mIPO

1iq1 – mIPO NLS-binding + autoinhibitory peptide domains
4e4v – hIPO NLS-binding domain (mutant) - human

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-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

IPO-13

2x19 – hIPO + GTPase Ran

2xwu – hIPO + UBC9
3zjy – hIPO + GTPase Ran + EIF-1A

References