Global Profiling Lysine Reactivity and Ligandability with Oxidant‐Triggered Bioconjugation Chemistry

Due to the high abundance and diverse functions of lysine residues, both in the interior and on the surface of proteins, the development of new methods to characterize their reactivity and ligandability could significantly expand the pool of druggable targets. To date, only a limited number of aminophilic electrophiles have been assessed for interactions with the lysine proteome, resulting in a substantial fraction remaining inaccessible to current probes. Here, to the best of our knowledge, we report the first oxidant‐triggered bioconjugation platform for in‐depth profiling of lysines. We quantified over 7000 covalently modifiable lysine residues, which significantly expands the coverage of ligandable lysines in the whole proteome. Chemical proteomics enabled the mapping of more than 100 endogenous kinases, thus providing a comprehensive landscape of ligandable catalytic lysines within the kinome. Moreover, we identified a suite of new ligandable lysines such as K60 of ENO1 and K31 of PPIA, offering insights for exploring new functional and targetable residues. These findings could provide valuable clues for the development of novel targeted covalent inhibitors (TCIs).