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==Crystal structure of E. coli Exonuclease I in complex with a dA16 oligonucleotide==
<StructureSection load='4js4' size='340' side='right'caption='[[4js4]], [[Resolution|resolution]] 3.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4js4]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli_K-12 Escherichia coli K-12]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4JS4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4JS4 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]] 3.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></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=4js4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4js4 OCA], [https://pdbe.org/4js4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4js4 RCSB], [https://www.ebi.ac.uk/pdbsum/4js4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4js4 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/EX1_ECOLI EX1_ECOLI] Also functions as a DNA deoxyribophosphodiesterase that releases deoxyribose-phosphate moieties following the cleavage DNA at an apurinic/apyrimidinic (AP) site by either an AP endonuclease AP lyase.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Escherichia coli Exonuclease I (ExoI) digests single-stranded DNA (ssDNA) in the 3'-5' direction in a highly processive manner. The crystal structure of ExoI, determined previously in the absence of DNA, revealed a C-shaped molecule with three domains that form a central positively charged groove. The active site is at the bottom of the groove, while an extended loop, proposed to encircle the DNA, crosses over the groove. Here, we present crystal structures of ExoI in complex with four different ssDNA substrates. The structures all have the ssDNA bound in essentially the predicted manner, with the 3'-end in the active site and the downstream end under the crossover loop. The central nucleotides of the DNA form a prominent bulge that contacts the SH3-like domain, while the nucleotides at the downstream end of the DNA form extensive interactions with an 'anchor' site. Seven of the complexes are similar to one another, but one has the ssDNA bound in a distinct conformation. The highest-resolution structure, determined at 1.95 A, reveals an Mg2+ ion bound to the scissile phosphate in a position corresponding to MgB in related two-metal nucleases. The structures provide new insights into the mechanism of processive digestion that will be discussed.

Crystal structures of Escherichia coli exonuclease I in complex with single-stranded DNA provide insights into the mechanism of processive digestion.,Korada SK, Johns TD, Smith CE, Jones ND, McCabe KA, Bell CE Nucleic Acids Res. 2013 Apr 22. PMID:23609540<ref>PMID:23609540</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 4js4" style="background-color:#fffaf0;"></div>

==See Also==
*[[Exonuclease 3D structures|Exonuclease 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Escherichia coli K-12]]
[[Category: Large Structures]]
[[Category: Bell CE]]