Database accession: MF7000639
Name: Isoflavanone 4'-O-methyltransferase with SAH and 2,7,4'-trihydroxyisoflavanone
PDB ID: 1zg3
Experimental method: X-ray (2.35 Å)
Assembly: Homodimer
Source organism: Medicago truncatula
Primary publication of the structure:
Liu CJ, Deavours BE, Richard SB, Ferrer JL, Blount JW, Huhman D, Dixon RA, Noel JP
Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses.
(2006) Plant Cell 18: 3656-69
PMID: 17172354
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.
Annotations from the GeneOntology database. Only terms that fit at least two of the interacting proteins are shown. Molecular function:
2,7,4'-trihydroxyisoflavanone-4'-O-methyltransferase activity 2,7,4'-trihydroxyisoflavanone-4'-O-methyltransferase activity
isoflavone 4'-O-methyltransferase activity isoflavone 4'-O-methyltransferase activity
O-methyltransferase activity O-methyltransferase activity
protein dimerization activity protein dimerization activity
Biological process:
aromatic compound biosynthetic process obsolete aromatic compound biosynthetic process
methylation methylation
Cellular component: not assigned
Structural annotations of the participating protein chains.Entry contents: 2 distinct polypeptide molecules
Chains: A, A-2
Notes: All chains according to the most probable oligomerization state stored in PDBe were considered.
Number of unique protein segments: 1
Name: Isoflavone 4'-O-methyltransferase
Source organism: Medicago truncatula
Length: 364 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMAFSTNGSEESELYHAQIHLYKHVYNFVSSMALKSAMELGIADAIHNHGKPMTLSELASSLKLHPSKVNILHRFLRLLTHNGFFAKTIVKGKEGDEEEEIAYSLTPPSKLLISGKPTCLSSIVKGALHPSSLDMWSSSKKWFNEDKEQTLFECATGESFWDFLNKDSESSTLSMFQDAMASDSRMFKLVLQENKRVFEGLESLVDVGGGTGGVTKLIHEIFPHLKCTVFDQPQVVGNLTGNENLNFVGGDMFKSIPSADAVLLKWVLHDWNDEQSLKILKNSKEAISHKGKDGKVIIIDISIDETSDDRGLTELQLDYDLVMLTMFLGKERTKQEWEKLIYDAGFSSYKITPISGFKSLIEVYP
UniProtKB AC: Q29U70 (positions: 7-364)
Coverage: 98%
Name: Isoflavone 4'-O-methyltransferase
Source organism: Medicago truncatula
Length: 364 residues
Sequence:Sequence according to the corresponding UniProt protein segmentMAFSTNGSEESELYHAQIHLYKHVYNFVSSMALKSAMELGIADAIHNHGKPMTLSELASSLKLHPSKVNILHRFLRLLTHNGFFAKTIVKGKEGDEEEEIAYSLTPPSKLLISGKPTCLSSIVKGALHPSSLDMWSSSKKWFNEDKEQTLFECATGESFWDFLNKDSESSTLSMFQDAMASDSRMFKLVLQENKRVFEGLESLVDVGGGTGGVTKLIHEIFPHLKCTVFDQPQVVGNLTGNENLNFVGGDMFKSIPSADAVLLKWVLHDWNDEQSLKILKNSKEAISHKGKDGKVIIIDISIDETSDDRGLTELQLDYDLVMLTMFLGKERTKQEWEKLIYDAGFSSYKITPISGFKSLIEVYP
UniProtKB AC: Q29U70 (positions: 7-364)
Coverage: 98%
Evidence demonstrating that the participating proteins are unstructured prior to the interaction and their folding is coupled to binding. Representative domain in related structures: Dimeric O-methyltransferase
Evidence level: Indirect evidence
Evidence coverage: Only some parts of the structure participates in mutual synergistic folding.
Complex Evidence:
Coniferyl alcohol 9-O-methyltransferase has an intertwined dimeric structure with large relative interaction surface. The active site is formed by both monomers and thus dimerization is critical for activity. The N-terminal helices form the dimerization subdomain and at the same time form the rear wall of the active-site cavity in the neighbouring monomer (PMID:23633600). Other 9-O-methyltransferase structures show similar features and exhibit no monomeric form in solution (PMID:11224575).
Chain A:
N/A
Chain A-2:
N/A
Surface and contacts features:
Structures from the PDB that contain the same number of proteins, and the proteins from the two structures show a sufficient degree of pairwise similarity, i.e. they belong to the same UniRef90 cluster (the full proteins exhibit at least 90% sequence identity) and convey roughly the same region to their respective interactions (the two regions from the two proteins share a minimum of 70% overlap). Download the CIF file (.cif)
Download this entry's XML file (.xml)
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