4uae

Structural highlights

Function

[IMA3_HUMAN] 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 non-classical NLS. [PB2_I75A3] Involved in transcription initiation and cap-stealing mechanism, in which cellular capped pre-mRNA are used to generate primers for viral transcription. Binds the cap of the target pre-RNA which is subsequently cleaved by PB1. May play a role in genome replication (By similarity).

See Also

• Importin 3D structures
• RNA polymerase

References

1. ↑ Pumroy RA, Ke S, Hart DJ, Zachariae U, Cingolani G. Molecular Determinants for Nuclear Import of Influenza A PB2 by Importin alpha Isoforms 3 and 7. Structure. 2015 Feb 3;23(2):374-84. doi: 10.1016/j.str.2014.11.015. Epub 2015 Jan, 15. PMID:25599645 doi:http://dx.doi.org/10.1016/j.str.2014.11.015