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Redox‐regulated methionine oxidation of Arabidopsis thaliana glutathione transferase Phi9 induces H‐site flexibility
Author(s) -
Tossounian MariaArmineh,
Wahni Khadija,
Van Molle Inge,
Vertommen Didier,
Astolfi Rosado Leonardo,
Messens Joris
Publication year - 2019
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.3440
Subject(s) - methionine sulfoxide reductase , chemistry , glutathione , arabidopsis thaliana , cysteine , methionine , active site , methionine sulfoxide , biochemistry , redox , binding site , arabidopsis , substrate (aquarium) , sulfoxide , transferase , stereochemistry , enzyme , biophysics , amino acid , mutant , biology , organic chemistry , ecology , gene
Glutathione transferase enzymes help plants to cope with biotic and abiotic stress. They mainly catalyze the conjugation of glutathione (GSH) onto xenobiotics, and some act as glutathione peroxidase. With X‐ray crystallography, kinetics, and thermodynamics, we studied the impact of oxidation on Arabidopsis thaliana glutathione transferase Phi 9 (GSTF9). GSTF9 has no cysteine in its sequence, and it adopts a universal GST structural fold characterized by a typical conserved GSH‐binding site (G‐site) and a hydrophobic co‐substrate‐binding site (H‐site). At elevated H 2 O 2 concentrations, methionine sulfur oxidation decreases its transferase activity. This oxidation increases the flexibility of the H‐site loop, which is reflected in lower activities for hydrophobic substrates. Determination of the transition state thermodynamic parameters shows that upon oxidation an increased enthalpic penalty is counterbalanced by a more favorable entropic contribution. All in all, to guarantee functionality under oxidative stress conditions, GSTF9 employs a thermodynamic and structural compensatory mechanism and becomes substrate of methionine sulfoxide reductases, making it a redox‐regulated enzyme.