View source for 6ukh


==HhaI endonuclease in Complex with DNA in space group P41212 (pH 6.0)==
<StructureSection load='6ukh' size='340' side='right'caption='[[6ukh]], [[Resolution|resolution]] 2.82&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6ukh]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Haemophilus_parahaemolyticus Haemophilus parahaemolyticus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6UKH OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6UKH 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]] 2.82&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</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=6ukh FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6ukh OCA], [https://pdbe.org/6ukh PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6ukh RCSB], [https://www.ebi.ac.uk/pdbsum/6ukh PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6ukh ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/I3DBY6_HAEPH I3DBY6_HAEPH] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
HhaI, a Type II restriction endonuclease, recognizes the symmetric sequence 5'-GCG downward arrowC-3' in duplex DNA and cleaves (' downward arrow') to produce fragments with 2-base, 3'-overhangs. We determined the structure of HhaI in complex with cognate DNA at an ultra-high atomic resolution of 1.0 A. Most restriction enzymes act as dimers with two catalytic sites, and cleave the two strands of duplex DNA simultaneously, in a single binding event. HhaI, in contrast, acts as a monomer with only one catalytic site, and cleaves the DNA strands sequentially, one after the other. HhaI comprises three domains, each consisting of a mixed five-stranded beta sheet with a defined function. The first domain contains the catalytic-site; the second contains residues for sequence recognition; and the third contributes to non-specific DNA binding. The active-site belongs to the 'PD-D/EXK' superfamily of nucleases and contains the motif SD-X11-EAK. The first two domains are similar in structure to two other monomeric restriction enzymes, HinP1I (G downward arrowCGC) and MspI (C downward arrowCGG), which produce fragments with 5'-overhangs. The third domain, present only in HhaI, shifts the positions of the recognition residues relative to the catalytic site enabling this enzyme to cleave the recognition sequence at a different position. The structure of M.HhaI, the biological methyltransferase partner of HhaI, was determined earlier. Together, these two structures represent the first natural pair of restriction-modification enzymes to be characterized in atomic detail.

Structure of HhaI endonuclease with cognate DNA at an atomic resolution of 1.0 A.,Horton JR, Yang J, Zhang X, Petronzio T, Fomenkov A, Wilson GG, Roberts RJ, Cheng X Nucleic Acids Res. 2019 Dec 27. pii: 5687824. doi: 10.1093/nar/gkz1195. PMID:31879785<ref>PMID:31879785</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6ukh" style="background-color:#fffaf0;"></div>

==See Also==
*[[Endonuclease 3D structures|Endonuclease 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Haemophilus parahaemolyticus]]
[[Category: Large Structures]]
[[Category: Cheng X]]
[[Category: Horton JR]]