1i8b

<table><tr><td colspan='2'>[[1i8b]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Alfalfa Alfalfa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1I8B OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1I8B FirstGlance]. <br>

</td></tr><tr id='NonStdRes'><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=CSD:3-SULFINOALANINE'>CSD</scene></td></tr>

<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1bi5|1bi5]], [[1i86|1i86]], [[1i88|1i88]], [[1i89|1i89]]</td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Naringenin-chalcone_synthase Naringenin-chalcone synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.74 2.3.1.74] </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=1i8b FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1i8b OCA], [http://pdbe.org/1i8b PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1i8b RCSB], [http://www.ebi.ac.uk/pdbsum/1i8b PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1i8b ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/CHS2_MEDSA CHS2_MEDSA]] The primary product of this enzyme is 4,2',4',6'-tetrahydroxychalcone (also termed naringenin-chalcone or chalcone) which can under specific conditions spontaneously isomerize into naringenin.<ref>PMID:10653632</ref> <ref>PMID:11732902</ref> <ref>PMID:11959984</ref> <ref>PMID:15380179</ref>

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== Publication Abstract from PubMed ==

Chalcone synthase (CHS) belongs to the family of type III polyketide synthases (PKS) that catalyze formation of structurally diverse polyketides. CHS synthesizes a tetraketide by sequential condensation of three acetyl anions derived from malonyl-CoA decarboxylation to a p-coumaroyl moiety attached to an active site cysteine. Gly256 resides on the surface of the CHS active site that is in direct contact with the polyketide chain derived from malonyl-CoA. Thus, position 256 serves as an ideal target to probe the link between cavity volume and polyketide chain-length determination in type III PKS. Functional examination of CHS G256A, G256V, G256L, and G256F mutants reveals altered product profiles from that of wild-type CHS. With p-coumaroyl-CoA as a starter molecule, the G256A and G256V mutants produce notably more tetraketide lactone. Further restrictions in cavity volume such as that seen in the G256L and G256F mutants yield increasing levels of the styrylpyrone bis-noryangonin from a triketide intermediate. X-ray crystallographic structures of the CHS G256A, G256V, G256L, and G256F mutants establish that these substitutions reduce the size of the active site cavity without significant alterations in the conformations of the polypeptide backbones. The side chain volume of position 256 influences both the number of condensation reactions during polyketide chain extension and the conformation of the triketide and tetraketide intermediates during the cyclization reaction. These results viewed in conjunction with the natural sequence variation of residue 256 suggest that rapid diversification of product specificity without concomitant loss of substantial catalytic activity in related CHS-like enzymes can occur by site-specific evolution of side chain volume at position 256.

 

<div class="pdbe-citations 1i8b" style="background-color:#fffaf0;"></div>

[[Category: Alfalfa]]

[[Category: Naringenin-chalcone synthase]]

[[Category: Bowman, M E]]

[[Category: Jez, J M]]

[[Category: Noel, J P]]

[[Category: Transferase]]