View source for 2qwx


==Crystal Structure of Quinone Reductase II==
<StructureSection load='2qwx' size='340' side='right' caption='[[2qwx]], [[Resolution|resolution]] 1.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2qwx]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Human Human]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2QWX OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2QWX FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=FAD:FLAVIN-ADENINE+DINUCLEOTIDE'>FAD</scene>, <scene name='pdbligand=ML1:N-[2-(5-METHOXY-1H-INDOL-3-YL)ETHYL]ACETAMIDE'>ML1</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1sg0|1sg0]]</td></tr>
<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">NQO2, NMOR2 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=9606 HUMAN])</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Ribosyldihydronicotinamide_dehydrogenase_(quinone) Ribosyldihydronicotinamide dehydrogenase (quinone)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.10.99.2 1.10.99.2] </span></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2qwx FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2qwx OCA], [http://pdbe.org/2qwx PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=2qwx RCSB], [http://www.ebi.ac.uk/pdbsum/2qwx PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=2qwx ProSAT]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/NQO2_HUMAN NQO2_HUMAN]] The enzyme apparently serves as a quinone reductase in connection with conjugation reactions of hydroquinones involved in detoxification pathways as well as in biosynthetic processes such as the vitamin K-dependent gamma-carboxylation of glutamate residues in prothrombin synthesis.<ref>PMID:18254726</ref>  
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/qw/2qwx_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=2qwx ConSurf].
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== Publication Abstract from PubMed ==
Melatonin exerts its biological effects through at least two transmembrane G-protein-coupled receptors, MT1 and MT2, and a lower-affinity cytosolic binding site, designated MT3. MT3 has recently been identified as QR2 (quinone reductase 2) (EC 1.10.99.2) which is of significance since it links the antioxidant effects of melatonin to a mechanism of action. Initially, QR2 was believed to function analogously to QR1 in protecting cells from highly reactive quinones. However, recent studies indicate that QR2 may actually transform certain quinone substrates into more highly reactive compounds capable of causing cellular damage. Therefore it is hypothesized that inhibition of QR2 in certain cases may lead to protection of cells against these highly reactive species. Since melatonin is known to inhibit QR2 activity, but its binding site and mode of inhibition are not known, we determined the mechanism of inhibition of QR2 by melatonin and a series of melatonin and 5-hydroxytryptamine (serotonin) analogues, and we determined the X-ray structures of melatonin and 2-iodomelatonin in complex with QR2 to between 1.5 and 1.8 A (1 A=0.1 nm) resolution. Finally, the thermodynamic binding constants for melatonin and 2-iodomelatonin were determined by ITC (isothermal titration calorimetry). The kinetic results indicate that melatonin is a competitive inhibitor against N-methyldihydronicotinamide (K(i)=7.2 microM) and uncompetitive against menadione (K(i)=92 microM), and the X-ray structures shows that melatonin binds in multiple orientations within the active sites of the QR2 dimer as opposed to an allosteric site. These results provide new insights into the binding mechanisms of melatonin and analogues to QR2.

Kinetic, thermodynamic and X-ray structural insights into the interaction of melatonin and analogues with quinone reductase 2.,Calamini B, Santarsiero BD, Boutin JA, Mesecar AD Biochem J. 2008 Jul 1;413(1):81-91. PMID:18254726<ref>PMID:18254726</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Quinone reductase|Quinone reductase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Human]]
[[Category: Boutin, J A]]
[[Category: Calamini, B]]
[[Category: Mesecar, A D]]
[[Category: Santarsiero, B D]]
[[Category: Fad]]
[[Category: Flavoprotein]]
[[Category: Metal-binding]]
[[Category: Oxidoreductase]]
[[Category: Qr2]]