Proteome-Wide Survey Reveals Norbornene Is Complementary to Dimedone and Related Nucleophilic Probes for Cysteine Sulfenic Acid

Detection of cysteine sulfenic acid in live cells is critical in advancing our understanding of cysteine redox chemistry and its biological function. Accordingly, there is a need to develop sulfenic acid-specific chemical probes with distinct reaction mechanisms to facilitate proteome-wide detection of this important posttranslational modification. Herein, we report the first whole-cell proteomics analysis using a norbornene probe to detect cysteine sulfenic acid in live HeLa cells. Comparison of the enriched proteins to those identified using dimedone and other C -nucleophilic probes revealed a complementary reactivity profile. Remarkably, 148 new members of the sulfenome were identified. These discoveries highlight how subtle differences in chemical reactivity of both the probes and cysteine residues influence detection. Overall, this study expands our understanding of protein oxidation at cysteine and reveals new proteins to consider for future studies of cysteine oxidation, redox regulation and signaling, and the biochemistry of oxidative stress.