Importin Alpha 6 Subunit

From Anvita Health Wiki

Contents 1 Function 2 Structure 3 Compartment 4 Expression 5 More General Terms 6 Additional Terms 7 Internet Database 8 References

Function

• nuclear protein import as an adapter protein for nuclear receptor KPNB1
• binds specifically & directly to substrates containing either a simple or bipartite NLS motif
• docking of the importin/substrate complex to the nuclear pore complex is mediated by KPNB1 through binding to nucleoporin FxFG repeats
• 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 importin-beta & the 3 components separate
• importin-alpha & importin-beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin
• 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
• mediates nuclear import of STAT1 homodimers & STAT1/STAT2 heterodimers by recognizing non-classical NLSs of STAT1 & STAT2 through ARM repeats 8-9
• recognizes influenza A virus nucleoprotein through ARM repeat 7-9
• in vitro, mediates the nuclear import of human cytomegalovirus
• UL84 by recognizing a non-classical NLS
• forms a complex with importin subunit beta-1

Structure

• consists of

• N-terminal hydrophilic region
• hydrophobic central region composed of 10 repeats
• short hydrophilic C-terminus

• N-terminal hydrophilic region contains the importin beta binding domain (IBB domain), which is sufficient for binding importin beta & essential for nuclear protein import
• 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 & 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 ( putative)
• the major & minor NLS binding sites

• mainly involved in recognition of simple or bipartite NLS motifs
• structurally located within in a helical surface groove
• they contain several conserved Trp & Asn of the corresponding 3rd helices ( H3) of ARM repeats which mainly contribute to binding

• belongs to the importin alpha family
• contains 10 ARM repeats
• contains 1 IBB domain

Compartment

• cytoplasm

Expression

• testis

More General Terms

• importin alpha subunit

Additional Terms

• importin complex (NLS-binding protein)

Internet Database

OMIM: 604545
Prosite: [1]
UniProt: [2]
Entrez gene: 3841

References

1. UniProt [3]

importin alpha-6 subunit (karyopherin alpha-5 subunit, KPNA5)