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| - | [[Image:1zg3.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1zg3| PDB=1zg3 | SCENE= }} | | {{STRUCTURE_1zg3| PDB=1zg3 | SCENE= }} |
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| - | '''Crystal structure of the isoflavanone 4'-O-methyltransferase complexed with SAH and 2,7,4'-trihydroxyisoflavanone'''
| + | ===Crystal structure of the isoflavanone 4'-O-methyltransferase complexed with SAH and 2,7,4'-trihydroxyisoflavanone=== |
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| - | ==Overview==
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| - | In leguminous plants such as pea (Pisum sativum), alfalfa (Medicago sativa), barrel medic (Medicago truncatula), and chickpea (Cicer arietinum), 4'-O-methylation of isoflavonoid natural products occurs early in the biosynthesis of defense chemicals known as phytoalexins. However, among these four species, only pea catalyzes 3-O-methylation that converts the pterocarpanoid isoflavonoid 6a-hydroxymaackiain to pisatin. In pea, pisatin is important for chemical resistance to the pathogenic fungus Nectria hematococca. While barrel medic does not biosynthesize 6a-hydroxymaackiain, when cell suspension cultures are fed 6a-hydroxymaackiain, they accumulate pisatin. In vitro, hydroxyisoflavanone 4'-O-methyltransferase (HI4'OMT) from barrel medic exhibits nearly identical steady state kinetic parameters for the 4'-O-methylation of the isoflavonoid intermediate 2,7,4'-trihydroxyisoflavanone and for the 3-O-methylation of the 6a-hydroxymaackiain isoflavonoid-derived pterocarpanoid intermediate found in pea. Protein x-ray crystal structures of HI4'OMT substrate complexes revealed identically bound conformations for the 2S,3R-stereoisomer of 2,7,4'-trihydroxyisoflavanone and the 6aR,11aR-stereoisomer of 6a-hydroxymaackiain. These results suggest how similar conformations intrinsic to seemingly distinct chemical substrates allowed leguminous plants to use homologous enzymes for two different biosynthetic reactions. The three-dimensional similarity of natural small molecules represents one explanation for how plants may rapidly recruit enzymes for new biosynthetic reactions in response to changing physiological and ecological pressures.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_17172354}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 17172354 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_17172354}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Isoflavanone 4'-o-methyltransferase]] | | [[Category: Isoflavanone 4'-o-methyltransferase]] |
| | [[Category: Rossman fold]] | | [[Category: Rossman fold]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:34:37 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 17:31:23 2008'' |
Revision as of 14:31, 27 July 2008
Template:STRUCTURE 1zg3
Crystal structure of the isoflavanone 4'-O-methyltransferase complexed with SAH and 2,7,4'-trihydroxyisoflavanone
Template:ABSTRACT PUBMED 17172354
About this Structure
1ZG3 is a Single protein structure of sequence from Medicago truncatula. Full crystallographic information is available from OCA.
Reference
Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses., Liu CJ, Deavours BE, Richard SB, Ferrer JL, Blount JW, Huhman D, Dixon RA, Noel JP, Plant Cell. 2006 Dec;18(12):3656-69. Epub 2006 Dec 15. PMID:17172354
Page seeded by OCA on Sun Jul 27 17:31:23 2008
