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Disulfide bond formation protects Arabidopsis thaliana glutathione transferase tau 23 from oxidative damage

DOI: 10.1016/j.bbagen.2017.10.007 DOI Help

Authors: Maria-armineh Tossounian (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) , Khadija Wahni (VIB-VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Silke Jacques (VIB-UGent Center for Medical Biotechnology; Ghent University; VIB-UGent Center for Plant Systems Biology; Ghent University) , Kris Gevaert (VIB-UGent Center for Medical Biotechnology; Ghent University) , Frank Van Breusegem (VIB-UGent Center for Plant Systems Biology; Ghent University) , Didier Vertommen (Université Catholique de Louvain) , David Young (VIB-VUB Center for Structural Biology; Brussels Center for Redox Biology; Vrije Universiteit Brussel) , Leonardo Astolfi Rosado (VIB-VUB Center for Structural Biology) , 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: Biochimica Et Biophysica Acta (bba) - General Subjects

State: Published (Approved)
Published: October 2017

Abstract: Background Glutathione transferases play an important role as detoxifying enzymes. In A. thaliana, elevated levels of reactive oxygen species (ROS), provoked during biotic and abiotic stress, influence the activity of GSTU23. The aim of this study is to determine the impact of oxidative stress on the function and structure of GSTU23. Methods The impact of oxidation on the function of GSTU23 was studied using a glutathione transferase biochemical assay and mass spectrometry. With kinetics, circular dichroism and thermodynamics, we compared reduced with oxidized GSTU23. X-ray crystal structures of GSTU23 visualize the impacts of oxidation on methionines and cysteines. Results In the presence of 100 μM H2O2, oxidation of the methionine side-chain to a sulfoxide is the prominent post-translational modification, which can be reduced by C. diphtheriae MsrA and MsrB. However, increasing the level to 200 μM H2O2 results in a reversible intramolecular disulfide between Cys65-Cys110, which is substrate for glutaredoxin. Under these oxidizing conditions, GSTU23 undergoes a structural change and forms a more favourable enzyme-substrate complex to overcome kcat decrease. Conclusions and significance At lower H2O2 levels (100 μM), GSTU23 forms methionine sulfoxides. Specifically, oxidation of Met14, located near the catalytic Ser13, could interfere with both GSH binding and catalytic activation. At higher H2O2 levels (200 μM), the Cys65-Cys110 disulfide bond protects other cysteines and also methionines from overoxidation. This study shows the impact of oxidative stress on GSTU23 regulated by methionine sulfoxide reductases and glutaredoxin, and the mechanisms involved in maintaining its catalytic functionality under oxidizing conditions.

Journal Keywords: Glutathione transferase; Kinetics; X-ray structure; Thermodynamics; Methionine sulfoxide; Disulfide bond

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I04-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography