Ninhydrin as a Covalent Warhead for Chemical Proteomic-Enabled Discovery and Selective Engagement of Reactive Arginines

Chemical proteomic methods to screen for reactive proteinaceous amino acids have transformed small-molecule discovery pipelines, but their application remains mostly limited to sites where reactive cysteines and lysines are present. Here we report a ninhydrin-based warhead that selectively modifies arginine residues, thus expanding the repertoire of amino acids targetable by covalent molecules.

Specifically, we developed alkyne-functionalized variants of ninhydrin to establish an arginine-specific chemical proteomics platform, enabling the classification of more than 6,800 unique reactive arginines from one cell line. These studies uncovered potential modification sites on disease-relevant proteins, including reactive arginines within catalytic sites that are essential for function and reactive arginines on proteins lacking reactive cysteines.