1fm7

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[[Image:1fm7.jpg|left|200px]]<br /><applet load="1fm7" size="350" color="white" frame="true" align="right" spinBox="true"
 
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caption="1fm7, resolution 2.3&Aring;" />
 
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'''CHALCONE ISOMERASE COMPLEXED WITH 5-DEOXYFLAVANONE'''<br />
 
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==Overview==
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==CHALCONE ISOMERASE COMPLEXED WITH 5-DEOXYFLAVANONE==
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Chalcone isomerase (CHI) catalyzes the intramolecular cyclization of bicyclic chalcones into tricyclic (S)-flavanones. The activity of CHI is essential for the biosynthesis of flavanone precursors of floral pigments and phenylpropanoid plant defense compounds. We have examined the spontaneous and CHI-catalyzed cyclization reactions of 4,2',4',6'-tetrahydroxychalcone, 4,2',4'-trihydroxychalcone, 2',4'-dihydroxychalcone, and 4,2'-dihydroxychalcone into the corresponding flavanones. The pH dependence of flavanone formation indicates that both the non-enzymatic and enzymatic reactions first require the bulk phase ionization of the substrate 2'-hydroxyl group and subsequently on the reactivity of the newly formed 2'-oxyanion during C-ring formation. Solvent viscosity experiments demonstrate that at pH 7.5 the CHI-catalyzed cyclization reactions of 4,2',4',6'-tetrahydroxychalcone, 4,2',4'-trihydroxychalcone, and 2',4'-dihydroxychalcone are approximately 90% diffusion-controlled, whereas cyclization of 4,2'-dihydroxychalcone is limited by a chemical step that likely reflects the higher pK(a) of the 2'-hydroxyl group. At pH 6.0, the reactions with 4,2',4',6'-tetrahydroxychalcone and 4,2',4'-trihydroxychalcone are approximately 50% diffusion-limited, whereas the reactions of both dihydroxychalcones are limited by chemical steps. Comparisons of the 2.1-2.3 A resolution crystal structures of CHI complexed with the products 7,4'-dihydroxyflavanone, 7-hydroxyflavanone, and 4'-hydroxyflavanone show that the 7-hydroxyflavanones all share a common binding mode, whereas 4'-hydroxyflavanone binds in an altered orientation at the active site. Our functional and structural studies support the proposal that CHI accelerates the stereochemically defined intramolecular cyclization of chalcones into biologically active (2S)-flavanones by selectively binding an ionized chalcone in a conformation conducive to ring closure in a diffusion-controlled reaction.
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<StructureSection load='1fm7' size='340' side='right'caption='[[1fm7]], [[Resolution|resolution]] 2.30&Aring;' scene=''>
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== Structural highlights ==
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==About this Structure==
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<table><tr><td colspan='2'>[[1fm7]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Medicago_sativa Medicago sativa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FM7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1FM7 FirstGlance]. <br>
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1FM7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Medicago_sativa Medicago sativa] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=DFV:'>DFV</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Chalcone_isomerase Chalcone isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.5.1.6 5.5.1.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FM7 OCA].
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.3&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=DFV:7-HYDROXY-2-(4-HYDROXY-PHENYL)-CHROMAN-4-ONE'>DFV</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr>
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==Reference==
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1fm7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1fm7 OCA], [https://pdbe.org/1fm7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1fm7 RCSB], [https://www.ebi.ac.uk/pdbsum/1fm7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1fm7 ProSAT]</span></td></tr>
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Reaction mechanism of chalcone isomerase. pH dependence, diffusion control, and product binding differences., Jez JM, Noel JP, J Biol Chem. 2002 Jan 11;277(2):1361-9. Epub 2001 Nov 6. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11698411 11698411]
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</table>
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[[Category: Chalcone isomerase]]
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== Function ==
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[https://www.uniprot.org/uniprot/CFI1_MEDSA CFI1_MEDSA] Catalyzes the intramolecular cyclization of bicyclic chalcones into tricyclic (S)-flavanones. Responsible for the isomerization of 4,2',4',6'-tetrahydroxychalcone (also termed chalcone) into naringenin.<ref>PMID:10966651</ref> <ref>PMID:11955065</ref> <ref>PMID:11698411</ref>
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/fm/1fm7_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</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=1fm7 ConSurf].
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<div style="clear:both"></div>
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== References ==
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<references/>
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__TOC__
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</StructureSection>
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[[Category: Large Structures]]
[[Category: Medicago sativa]]
[[Category: Medicago sativa]]
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[[Category: Single protein]]
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[[Category: Jez JM]]
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[[Category: Jez, J M.]]
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[[Category: Noel JP]]
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[[Category: Noel, J P.]]
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[[Category: DFV]]
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[[Category: SO4]]
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[[Category: chalcone]]
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[[Category: diffusion-limited]]
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[[Category: natural product biosynthesis]]
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[[Category: plant enzyme]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:40:10 2008''
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Current revision

CHALCONE ISOMERASE COMPLEXED WITH 5-DEOXYFLAVANONE

PDB ID 1fm7

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