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==Structure of Importin-4 bound to the H3-H4-ASF1 histone-histone chaperone complex==
<StructureSection load='7unk' size='340' side='right'caption='[[7unk]], [[Resolution|resolution]] 3.45&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[7unk]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens], [https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae] and [https://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=7UNK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=7UNK FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 3.45&#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=7unk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=7unk OCA], [https://pdbe.org/7unk PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=7unk RCSB], [https://www.ebi.ac.uk/pdbsum/7unk PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=7unk ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/IPO4_HUMAN IPO4_HUMAN] Functions in nuclear protein import as nuclear transport receptor. Serves as receptor for nuclear localization signals (NLS) in cargo substrates. Is thought to mediate docking of the importin/substrate complex to the nuclear pore complex (NPC) through binding to nucleoporin 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 the importin, the importin/substrate complex dissociates and importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran. 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 (By similarity). Mediates the nuclear import of RPS3A. In vitro, mediates the nuclear import of human cytomegalovirus UL84 by recognizing a non-classical NLS.<ref>PMID:11823430</ref> 
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== Publication Abstract from PubMed ==
IMPORTIN-4, the primary nuclear import receptor of core histones H3 and H4, binds the H3-H4 dimer and histone chaperone ASF1 prior to nuclear import. However, how H3-H3-ASF1 is recognized for transport cannot be explained by available crystal structures of IMPORTIN-4-histone tail peptide complexes. Our 3.5-A IMPORTIN-4-H3-H4-ASF1 cryoelectron microscopy structure reveals the full nuclear import complex and shows a binding mode different from suggested by previous structures. The N-terminal half of IMPORTIN-4 clamps the globular H3-H4 domain and H3 alphaN helix, while its C-terminal half binds the H3 N-terminal tail weakly; tail contribution to binding energy is negligible. ASF1 binds H3-H4 without contacting IMPORTIN-4. Together, ASF1 and IMPORTIN-4 shield nucleosomal H3-H4 surfaces to chaperone and import it into the nucleus where RanGTP binds IMPORTIN-4, causing large conformational changes to release H3-H4-ASF1. This work explains how full-length H3-H4 binds IMPORTIN-4 in the cytoplasm and how it is released in the nucleus.

Structure of IMPORTIN-4 bound to the H3-H4-ASF1 histone-histone chaperone complex.,Bernardes NE, Fung HYJ, Li Y, Chen Z, Chook YM Proc Natl Acad Sci U S A. 2022 Sep 20;119(38):e2207177119. doi: , 10.1073/pnas.2207177119. Epub 2022 Sep 14. PMID:36103578<ref>PMID:36103578</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 7unk" style="background-color:#fffaf0;"></div>

==See Also==
*[[Histone 3D structures|Histone 3D structures]]
*[[Importin 3D structures|Importin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Saccharomyces cerevisiae]]
[[Category: Xenopus laevis]]
[[Category: Bernardes NE]]
[[Category: Chen Z]]
[[Category: Chook YM]]
[[Category: Fung HYJ]]
[[Category: Li Y]]