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Redox regulated methionine oxidation of Arabidopsis thaliana glutathione transferase Phi9 induces H-site flexibility

DOI: 10.1002/pro.3440 DOI Help

Authors: Maria-armineh Tossounian (VIB‐VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Khadija Wahni (VIB‐VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Inge Van Molle (VIB‐VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Didier Vertommen (Université Catholique de Louvain) , Leonardo Astolfi Rosado (VIB‐VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Joris Messens (VIB‐VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Protein Science

State: Published (Approved)
Published: May 2018
Diamond Proposal Number(s): 9426

Abstract: Glutathione transferase enzymes help plants to cope with biotic and abiotic stress. They mainly catalyse 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 H2O2 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 favourable 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.

Journal Keywords: redox; methionine sulfoxide; X‐ray structure; methionine sulfoxide reductase; steady‐state kinetics; thermodynamics

Subject Areas: Biology and Bio-materials


Instruments: I04-Macromolecular Crystallography