View source for 6sjf


==Cryo-EM structure of the RecBCD Chi unrecognised complex==
<SX load='6sjf' size='340' side='right' viewer='molstar' caption='[[6sjf]], [[Resolution|resolution]] 3.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6sjf]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6SJF OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6SJF 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]] 3.9&#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=6sjf FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6sjf OCA], [https://pdbe.org/6sjf PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6sjf RCSB], [https://www.ebi.ac.uk/pdbsum/6sjf PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6sjf ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/RECB_ECOLI RECB_ECOLI] A helicase/nuclease that prepares dsDNA breaks (DSB) for recombinational DNA repair. Binds to DSBs and unwinds DNA via a rapid (>1 kb/second) and highly processive (>30 kb) ATP-dependent bidirectional helicase. Unwinds dsDNA until it encounters a Chi (crossover hotspot instigator, 5'-GCTGGTGG-3') sequence from the 3' direction. Cuts ssDNA a few nucleotides 3' to Chi site, by nicking one strand or switching the strand degraded (depending on the reaction conditions). The properties and activities of the enzyme are changed at Chi. The Chi-altered holoenzyme produces a long 3'-ssDNA overhang which facilitates RecA-binding to the ssDNA for homologous DNA recombination and repair. Holoenzyme degrades any linearized DNA that is unable to undergo homologous recombination (PubMed:4562392, PubMed:4552016, PubMed:123277). In the holoenzyme this subunit contributes ATPase, 3'-5' helicase, exonuclease activity and loads RecA onto ssDNA. The RecBC complex requires the RecD subunit for nuclease activity, but can translocate along ssDNA in both directions.<ref>PMID:10197988</ref> <ref>PMID:10518611</ref> <ref>PMID:10766864</ref> <ref>PMID:123277</ref> <ref>PMID:12815437</ref> <ref>PMID:12815438</ref> <ref>PMID:1535156</ref> <ref>PMID:16041061</ref> <ref>PMID:1618858</ref> <ref>PMID:16388588</ref> <ref>PMID:18079176</ref> <ref>PMID:20852646</ref> <ref>PMID:23851395</ref> <ref>PMID:25073102</ref> <ref>PMID:4268693</ref> <ref>PMID:4552016</ref> <ref>PMID:4562392</ref> <ref>PMID:7608206</ref> <ref>PMID:9192629</ref> <ref>PMID:9230304</ref> <ref>PMID:9448271</ref> <ref>PMID:9790841</ref> 
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== Publication Abstract from PubMed ==
The RecBCD complex plays key roles in phage DNA degradation, CRISPR array acquisition (adaptation) and host DNA repair. The switch between these roles is regulated by a DNA sequence called Chi. We report cryo-EM structures of the Escherichia coli RecBCD complex bound to several different DNA forks containing a Chi sequence, including one in which Chi is recognized and others in which it is not. The Chi-recognized structure shows conformational changes in regions of the protein that contact Chi and reveals a tortuous path taken by the DNA. Sequence specificity arises from interactions with both the RecC subunit and the sequence itself. These structures provide molecular details for how Chi is recognized and insights into the changes that occur in response to Chi binding that switch RecBCD from bacteriophage destruction and CRISPR spacer acquisition to constructive host DNA repair.

A conformational switch in response to Chi converts RecBCD from phage destruction to DNA repair.,Cheng K, Wilkinson M, Chaban Y, Wigley DB Nat Struct Mol Biol. 2020 Jan;27(1):71-77. doi: 10.1038/s41594-019-0355-2. Epub, 2020 Jan 6. PMID:31907455<ref>PMID:31907455</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 6sjf" style="background-color:#fffaf0;"></div>

==See Also==
*[[Exonuclease 3D structures|Exonuclease 3D structures]]
== References ==
<references/>
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</SX>
[[Category: Escherichia coli]]
[[Category: Large Structures]]
[[Category: Synthetic construct]]
[[Category: Cheng K]]
[[Category: Wigley DB]]
[[Category: Wilkinson M]]