6bvt
From Proteopedia
Importin alpha 1 in cargo free state
Structural highlights
Function[IMA1_MOUSE] 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. Publication Abstract from PubMedSeven human isoforms of importin alpha mediate nuclear import of cargo in a tissue- and isoform-specific manner. How nuclear import adaptors differentially interact with cargo harbouring the same nuclear localisation signal (NLS) remains poorly understood, as the NLS recognition region is highly conserved. Here, we provide a structural basis for the nuclear import specificity of W proteins in Hendra and Nipah viruses. We determine the structural interfaces of these cargo bound to importin alpha1 and alpha3, identifying a 2.4-fold more extensive interface and > 50-fold higher binding affinity for importin alpha3. Through the design of importin alpha1 and alpha3 chimeric and mutant proteins, together with structures of cargo-free importin alpha1 and alpha3 isoforms, we establish that the molecular basis of specificity resides in the differential positioning of the armadillo repeats 7 and 8. Overall, our study provides mechanistic insights into a range of important nucleocytoplasmic transport processes reliant on isoform adaptor specificity. Structural basis for importin alpha 3 specificity of W proteins in Hendra and Nipah viruses.,Smith KM, Tsimbalyuk S, Edwards MR, Cross EM, Batra J, Soares da Costa TP, Aragao D, Basler CF, Forwood JK Nat Commun. 2018 Sep 12;9(1):3703. doi: 10.1038/s41467-018-05928-5. PMID:30209309[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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