An Activity-Based Oxaziridine Platform for Identifying and Developing Covalent Ligands for Functional Allosteric Methionine Sites: Redox-Dependent Inhibition of Cyclin-Dependent Kinase 4

Activity-based protein profiling (ABPP) is a versatile strategy for enabling identification and characterization of new functional protein sites and discovery of lead compounds for therapeutic development. Yet, the vast majority of ABPP methods applied for covalent drug discovery target highly nucleophilic amino acids such as cysteine or lysine. Here, we report a methionine-directed ABPP platform using Redox-Activated Chemical Tagging (ReACT), which leverages a biomimetic oxidative ligation strategy for selective methionine modification. Application of ReACT to the cancer-driver protein cyclin-dependent kinase 4 (CDK4) as a representative high-value drug target identified three new hyperreactive, ligandable methionine residues, including an allosteric M169 site that is proximal to an activating T172 phosphorylation site. With this information in hand, we designed and synthesized a new methionine-targeting covalent ligand library based on oxaziridine fragments