Photocaged activity-based probes for improved monitoring of protein S-sulfenylation in living cells

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. A variety of activity-based probes have been developed to profile sulfenic acid in living cells. However, due to the transient presence and low content of sulfenic acid in living cell, high doses of probes are needed to achieve efficient labeling. More importantly, current probes have no temporal control over sulfenic acid labeling. To overcome these limitations, two caged cysteine sulfenic acid probes DYn-2-ONB and DYn-2-Cou with either an o-nitrobenzyl or coumarin protecting group were developed in this study. 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 for improved monitoring of protein S-sulfenylation in living cells.