The dynamics of protein-bound methionine oxidation events in Arabidopsis thaliana during oxidative stress

Reactive oxygen species such as hydrogen peroxide can modify proteins via direct oxidation of their sulfur-containing amino acids, cysteine and methionine. Methionine oxidation, studied here, is a reversible posttranslational modification, which is increasingly suggested as a mechanism by which proteins perceive oxidative stress and function in redox signalling. Identification of proteins with oxidized methionines is a first prerequisite towards understanding the functional effect of methionine oxidation on proteins and the biological processes in which they are involved. Here, we describe a proteome-wide study of in vivo protein-bound methionine oxidation in plants upon oxidative stress, using Arabidopsis thaliana catalase 2 knock-out plants as a model system. We identified approximately 500 sites of oxidation in about 400 proteins, and quantified the differences in oxidation between wild-type and catalase 2 knock-out plants. Further, by sampling over time, we mapped the dynamics of methionine oxidation and gained new insights into this complex and dynamic landscape of the part of the plant proteome that is sculpted by oxidative stress.