1zg3

[[Image:1zg3.gif|left|200px]]<br /><applet load="1zg3" size="350" color="white" frame="true" align="right" spinBox="true"

caption="1zg3, resolution 2.35&Aring;" />

'''Crystal structure of the isoflavanone 4'-O-methyltransferase complexed with SAH and 2,7,4'-trihydroxyisoflavanone'''<br />

==Overview==

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.

 

==About this Structure==

1ZG3 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Medicago_truncatula Medicago truncatula] with <scene name='pdbligand=2HI:'>2HI</scene> and <scene name='pdbligand=SAH:'>SAH</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ZG3 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:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17172354 17172354]

[[Category: Deavours, B.E.]]

[[Category: Dixon, R.A.]]

[[Category: Ferrer, J.L.]]

[[Category: Liu, C.J.]]

[[Category: Noel, J.P.]]

[[Category: Richard, S.]]