Senkane, K. et al. Angew. Chem. https://doi.org/10.1002/ange.201905829 (2019).

Small molecules and drugs that target active-site residues can be useful in clinical and biological applications. One class of small molecules is reversible covalent inhibitors, which allow sustained target engagement but entail lower immunogenicity risks and fewer off-target effects than irreversible covalent inhibitors. Senkane et al. describe a mass-spectrometry-based method for proteome-wide evaluation of reversible inhibitor targets. The method integrates gel filtration (GF) and activity-based protein profiling to evaluate cysteine residues for reversible and irreversible interactions with α-cyanoacrylamide fragments across the human proteome. The GF step after addition of the electrophile essentially reverses the interaction where it is not permanent, and a comparison of all targets versus post-GF targets reveals the reversible candidates. The experiment showed broad potential with proteins from several classes. In spite of the limitations, such as the fact that certain proteins may unfold during the GF stage, a comprehensive mapping of entire proteomes using a variety of electrophiles has promise for drug development.