Description:

Chemical-proteomic strategies to investigate reactive cysteines
Cysteine residues play diverse functional roles in proteins, including catalysis, metal-binding, structural stabilization and redox regulation. These functional cysteines are highly reactive and can be targeted by irreversible inhibitors. We aim to identify new functional cysteines within the human proteome and develop chemical probes to covalently modify these residues. To achieve this, we have developed a chemical-proteomic platform to identify cysteines that are highly sensitive to S-nitrosation, which is a posttranslational modification known to regulate protein activity and localization. We identified several previously unannotated cysteines and demonstrate that they allosterically regulate protein activity through S-nitrosation. In order to develop chemical probes to modify these and other functional cysteines in the proteome, a library of cysteine-reactive small-molecules was generated. Our initial library is based on a trifunctionalized 1,3,5-triazine scaffold, from which a potent and selective cysteine-reactive inhibitor for protein disulfide isomerase was identified. Our studies illustrate the potential of irreversible cysteine-targeted inhibitors as pharmacological agents for a large subsection of the proteome.