View source for 3sz5


==Crystal Structure of LHK-Exo in complex with 5-phosphorylated oligothymidine (dT)4==
<StructureSection load='3sz5' size='340' side='right'caption='[[3sz5]], [[Resolution|resolution]] 2.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3sz5]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Laribacter_hongkongensis_HLHK9 Laribacter hongkongensis HLHK9]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3SZ5 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3SZ5 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='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MG:MAGNESIUM+ION'>MG</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=3sz5 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3sz5 OCA], [https://pdbe.org/3sz5 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3sz5 RCSB], [https://www.ebi.ac.uk/pdbsum/3sz5 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3sz5 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/C1D7P6_LARHH C1D7P6_LARHH] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Alkaline exonuclease and single-strand DNA (ssDNA) annealing proteins (SSAPs) are key components of DNA recombination and repair systems within many prokaryotes, bacteriophages and virus-like genetic elements. The recently sequenced beta-proteobacterium Laribacter hongkongensis (strain HLHK9) encodes putative homologs of alkaline exonuclease (LHK-Exo) and SSAP (LHK-Bet) proteins on its 3.17 Mb genome. Here, we report the biophysical, biochemical and structural characterization of recombinant LHK-Exo protein. LHK-Exo digests linear double-stranded DNA molecules from their 5'-termini in a highly processive manner. Exonuclease activities are optimum at pH 8.2 and essentially require Mg(2+) or Mn(2+) ions. 5'-phosphorylated DNA substrates are preferred over dephosphorylated ones. The crystal structure of LHK-Exo was resolved to 1.9 A, revealing a 'doughnut-shaped' toroidal trimeric arrangement with a central tapered channel, analogous to that of lambda-exonuclease (Exo) from bacteriophage-lambda. Active sites containing two bound Mg(2+) ions on each of the three monomers were located in clefts exposed to this central channel. Crystal structures of LHK-Exo in complex with dAMP and ssDNA were determined to elucidate the structural basis for substrate recognition and binding. Through structure-guided mutational analysis, we discuss the roles played by various active site residues. A conserved two metal ion catalytic mechanism is proposed for this class of alkaline exonucleases.

Structural and functional insight into the mechanism of an alkaline exonuclease from Laribacter hongkongensis.,Yang W, Chen WY, Wang H, Ho JW, Huang JD, Woo PC, Lau SK, Yuen KY, Zhang Q, Zhou W, Bartlam M, Watt RM, Rao Z Nucleic Acids Res. 2011 Dec;39(22):9803-19. Epub 2011 Sep 5. PMID:21893587<ref>PMID:21893587</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 3sz5" style="background-color:#fffaf0;"></div>

==See Also==
*[[Exonuclease 3D structures|Exonuclease 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Laribacter hongkongensis HLHK9]]
[[Category: Bartlam M]]
[[Category: Chen WY]]
[[Category: Rao Z]]
[[Category: Wang H]]
[[Category: Watt RM]]
[[Category: Yang W]]
[[Category: Zhang Q]]
[[Category: Zhou W]]