1zhf: Difference between revisions

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[[Image:1zhf.gif|left|200px]]
{{Seed}}
[[Image:1zhf.png|left|200px]]


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{{STRUCTURE_1zhf|  PDB=1zhf  |  SCENE=  }}  
{{STRUCTURE_1zhf|  PDB=1zhf  |  SCENE=  }}  


'''Crystal structure of selenomethionine substituted isoflavanone 4'-O-methyltransferase'''
===Crystal structure of selenomethionine substituted isoflavanone 4'-O-methyltransferase===




==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.
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{{ABSTRACT_PUBMED_17172354}}


==About this Structure==
==About this Structure==
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[[Category: Richard, S.]]
[[Category: Richard, S.]]
[[Category: Isoflavanone 4'-o-methyltransferase,rossman fold]]
[[Category: Isoflavanone 4'-o-methyltransferase,rossman fold]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 17:37:29 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 17:04:41 2008''

Revision as of 14:04, 28 July 2008

File:1zhf.png

Template:STRUCTURE 1zhf

Crystal structure of selenomethionine substituted isoflavanone 4'-O-methyltransferase

Template:ABSTRACT PUBMED 17172354

About this Structure

1ZHF 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

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