Structure-function relationships of wheat flavone O-methyltransferase: Homology modeling, site-directed mutagenesis and regulation

摘要: Wheat (Triticum aestivum) O-methyltransferase (TaOMT2) catalyzes the sequential methylation of flavone,tricetin (5,7,3',4',5'-pentahydroxyflavone) to its 3'-methyl-(selgin), 3',5'-dimethyl-(tricin) and 3',4',5'-trimethyl ether derivatives, although tricin is major product this reaction. The novelty TaOMT2 perform three methylations tricetin as a substrate, chemopreventive properties product, tricin, compelling interest in protein’s structure-function relationships, prompted us further investigate novel protein at biochemical, molecular structural levels. A 3-D model was constructed using crystal structure highly homologous Medicago sativa caffeic acid/5-hydroxyferulic acid (MsCOMT) template with aim proposing mechanism for multiple methyl transfer reactions wheat. Homology modeling experiments which each substrates tricetin, selgin docked into revealed number amino residues putatively involved substrate binding catalysis. Results suggest that mediated by an extensive network H-bonds van der Waals interactions. Mutational analysis structurally-guided active site identified those possible reaction discussed. The biological significance also investigated analyzing expression, enzyme activity patterns different wheat developmental stages, response cold acclimation abiotic stresses such salt drought. show predominantly accumulates influorescences compared leaves, coinciding increased methyltransferase influorescence tissues. effect on reveals cold-acclimated winter leaves. In contrast, shows tendency decrease during acclimation. Other stresses, drought have no effects accumulation but slight activity. importance stages