Crystallographic and Functional Characterization of the Fluorodifen-Inducible Glutathione Transferase from Glycine Max Reveals an Active Site Topography Suited for Diphenylether Herbicides and a Novel L-Site.

摘要: Glutathione transferases (GSTs) from the tau class (GSTU) are unique to plants and have important roles in stress tolerance detoxification of herbicides crops weeds. A fluorodifen-induced GST isoezyme (GmGSTU4-4) belonging was purified Glycine max by affinity chromatography. This isoenzyme cloned expressed Escherichia coli, its structural catalytic properties were investigated. The structure GmGSTU4-4 determined at 1.75 resolution complex with S-(p-nitrobenzyl)-glutathione (Nb-GSH). enzyme adopts canonical fold but a number functionally differences. Compared other plant GSTs, three-dimensional primarily shows differences hydrophobic substrate binding site, linker segment C-terminal region. X-ray identifies key amino acid residues site (H-site) provides insights into specificity mechanism enzyme. highly active conjugating diphenylether herbicide fluorodifen. possible reaction pathway involving conjugation glutathione fluorodifen is described based on site-directed mutagenesis molecular modeling studies. serine residue (Ser13) present position that would allow it stabilise thiolate anion enhance nucleophilicity. Tyr107 Arg111 moieties modulate efficiency enzyme, participate k(cat) regulation affecting rate-limiting step reaction. hitherto undescribed ligand-binding (L-site) located surface pocket also found. formed conserved residues, suggesting may an functional role transfer delivery bound ligands, presumably specific protein receptors.