Systematic and Quantitative Assessment of Hydrogen Peroxide Reactivity With Cysteines Across Human Proteomes.

Protein cysteinyl residues are the mediators of hydrogen peroxide (H2 O2 )-dependent redox signaling. However, site-specific mapping of the selectivity and dynamics of these redox reactions in cells poses a major analytical challenge. Here we describe a chemoproteomic platform to systematically and quantitatively analyze the reactivity of thousands of cysteines toward H2 O2 in human cells. We identified >900 H2 O2 -sensitive cysteines, which are defined as the H2 O2 -dependent redoxome. Although redox sites associated with antioxidative and metabolic functions are consistent, most of the H2 O2 -dependent redoxome varies dramatically between different cells. Structural analyses reveal that H2 O2 -sensitive cysteines are less conserved than their redox-insensitive counterparts and display distinct sequence motifs, structural features, and potential for crosstalk with lysine modifications. Notably, our chemoproteomic platform also provides an opportunity to predict oxidation-triggered protein conformational changes. The data are freely accessible as a resource at https://redox.ncpsb.org/OXID/.