View source for 1iq1


==CRYSTAL STRUCTURE OF THE IMPORTIN-ALPHA(44-54)-IMPORTIN-ALPHA(70-529) COMPLEX==
<StructureSection load='1iq1' size='340' side='right'caption='[[1iq1]], [[Resolution|resolution]] 2.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1iq1]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IQ1 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1IQ1 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.8&#8491;</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1iq1 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1iq1 OCA], [https://pdbe.org/1iq1 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1iq1 RCSB], [https://www.ebi.ac.uk/pdbsum/1iq1 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1iq1 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/IMA1_MOUSE 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.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/iq/1iq1_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1iq1 ConSurf].
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== Publication Abstract from PubMed ==
Proteins containing the classical nuclear localization sequences (NLSs) are imported into the nucleus by the importin-alpha/beta heterodimer. Importin-alpha contains the NLS binding site, whereas importin-beta mediates the translocation through the nuclear pore. We characterized the interactions involving importin-alpha during nuclear import using a combination of biophysical techniques (biosensor, crystallography, sedimentation equilibrium, electrophoresis, and circular dichroism). Importin-alpha is shown to exist in a monomeric autoinhibited state (association with NLSs undetectable by biosensor). Association with importin-beta (stoichiometry, 1:1; K(D) = 1.1 x 10(-8) m) increases the affinity for NLSs; the importin-alpha/beta complex binds representative monopartite NLS (simian virus 40 large T-antigen) and bipartite NLS (nucleoplasmin) with affinities (K(D) = 3.5 x 10(-8) m and 4.8 x 10(-8) m, respectively) comparable with those of a truncated importin-alpha lacking the autoinhibitory domain (T-antigen NLS, K(D) = 1.7 x 10(-8) m; nucleoplasmin NLS, K(D) = 1.4 x 10(-8) m). The autoinhibitory domain (as a separate peptide) binds the truncated importin-alpha, and the crystal structure of the complex resembles the structure of full-length importin-alpha. Our results support the model of regulation of nuclear import mediated by the intrasteric autoregulatory sequence of importin-alpha and provide a quantitative description of the binding and regulatory steps during nuclear import.

Biophysical characterization of interactions involving importin-alpha during nuclear import.,Catimel B, Teh T, Fontes MR, Jennings IG, Jans DA, Howlett GJ, Nice EC, Kobe B J Biol Chem. 2001 Sep 7;276(36):34189-98. Epub 2001 Jul 11. PMID:11448961<ref>PMID:11448961</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1iq1" style="background-color:#fffaf0;"></div>

==See Also==
*[[Importin 3D structures|Importin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Mus musculus]]
[[Category: Catimel B]]
[[Category: Fontes MRM]]
[[Category: Jennings IG]]
[[Category: Kobe B]]
[[Category: Teh T]]