ACR-Based Probe for the Quantitative Profiling of Histidine Reactivity in the Human Proteome

The quantitative profiling of residue
reactivity in proteins
promotes
the discovery of covalent druggable targets for precise therapy. Histidine
(His) residues, accounting for more than 20% of the active sites in
enzymes, have not been systematically characterized for their reactivity,
due to lack of labeling probes. Herein, we report a chemical proteomics
platform for the site-specific quantitative analysis of His reactivity
by combination of acrolein (ACR) labeling and reversible hydrazine
chemistry enrichment. Based on this platform, in-depth characterization
of His residues was conducted for the human proteome, in which the
rich content of His residues (>8200) was quantified, including
317
His hyper-reactive residues. Intriguingly, it was observed that the
hyper-reactive residues were less likely to be the sites for phosphorylation,
and the possible mechanism of this antagonistic effect still needs
to be evaluated in further research. Based on the first comprehensive
map of His residue reactivity, many more residues could be adopted
as the bindable sites to disrupt the activities of a diverse number
of proteins; meanwhile, ACR derivatives could also be used as a novel
reactive warhead in the development of covalent inhibitors.