PDBsum entry: 1zg3

Plant protein, transferase

PDB id: 1zg3

Contents

Protein chain

358 a.a. *

Ligands

2HI

SAH

Waters ×108

* Residue conservation analysis

PDB id:

1zg3

Name:

Plant protein, transferase

Title:

Crystal structure of the isoflavanone 4'-o-methyltransferase with sah and 2,7,4'-trihydroxyisoflavanone

Structure:

Isoflavanone 4'-o-methyltransferase. Chain: a. Engineered: yes

Source:

Medicago truncatula. Barrel medic. Organism_taxid: 3880. Gene: omt. Expressed in: escherichia coli bl21. Expression_system_taxid: 511693.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.35Å R-factor: 0.218 R-free: 0.266

Authors:

C.-J.Liu,B.E.Deavours,S.Richard,J.-L.Ferrer,R.A.Dixon,J.P.No

Key ref:

C.J.Liu et al. (2006). Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses. Plant Cell, 18, 3656-3669. PubMed id: 17172354 DOI: 10.1105/tpc.106.041376

Date:

20-Apr-05 Release date: 01-Aug-06

Protein chain

Q29U70  (Q29U70_MEDTR) -  Isoflavone 4'-O-methyltransferase

Seq: 364 a.a.

Struc: 358 a.a.

Enzyme reactions

• Enzyme class 1: E.C.2.1.1.212 - 2,7,4'-trihydroxyisoflavanone 4'-O-methyltransferase.
• Reaction: S-adenosyl-L-methionine + 2,7,4'-trihydroxyisoflavanone = S-adenosyl-L- homocysteine + 2,7-dihydroxy-4'-methoxyisoflavanone

S-adenosyl-L-methionine + 2,7,4'-trihydroxyisoflavanone = S-adenosyl-L- homocysteine (Bound ligand (Het Group name = SAH) corresponds exactly) + 2,7-dihydroxy-4'-methoxyisoflavanone (Bound ligand (Het Group name = 2HI) matches with 85.71% similarity)

• Enzyme class 2: E.C.2.1.1.46 - Isoflavone 4'-O-methyltransferase.

Pathway:

• Reaction: S-adenosyl-L-methionine + a 4'-hydroxyisoflavone = S-adenosyl-L- homocysteine + a 4'-methoxyisoflavone
• Cofactor: Magnesium

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

 Gene Ontology (GO) functional annotation 

• Biological process: methylation (1 term)
• Biochemical function: transferase activity (5 terms)

reference

DOI no: 10.1105/tpc.106.041376

Plant Cell 18:3656-3669 (2006)

PubMed id: 17172354

Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses.

C.J.Liu, B.E.Deavours, S.B.Richard, J.L.Ferrer, J.W.Blount, D.Huhman, R.A.Dixon, J.P.Noel.

ABSTRACT

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.