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

Maria-Armineh Tossounian, Khadija Wahni, Inge Van Molle, Didier Vertommen, Leonardo Astolfi Rosado, Joris Messens

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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 2O 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.

Original languageEnglish
Pages (from-to)56-67
Number of pages12
JournalProtein Science
Volume28
Issue number1
DOIs
Publication statusPublished - 1 Jan 2019

Keywords

  • X-ray structure
  • methionine sulfoxide
  • methionine sulfoxide reductase
  • redox
  • steady-state kinetics
  • thermodynamics

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