Photocaged Activity-Based Probes for Spatiotemporal Detection of Protein S-sulfenylation in Living Cells

Protein cysteine residues have unique reactivity due to the low redox potential of its thiol side chain. Protein S-sulfenylation (protein sulfenic acid), as one of the most significant oxidative post-translational modifications (OxiPTMs), plays a vital role in regulating protein function. Due to the transient presence of sulfenic acid in living cell, many detecting methods have been limited. Activity-based probes provide powerful tools to elucidate this process, so their discovery has been at the forefront of redox biology. In this study, two caged cysteine sulfenic acid probes DYn-2-ONB, DYn-2-Cou with either an o-nitrobenzyl or coumarin protecting group were developed. Both probes can be efficiently uncaged via irradiation to produce the active C-nucleophile probe DYn-2. Labeling assay in living cells demonstrated DYn-2-ONB exhibited better labeling capacity compared with DYn-2, providing it as a powerful tool to detect protein S-sulfenylation in spatio-temporally controllable manner.