Sulfur-triazole exchange chemistry for the global targeting and liganding of functional tyrosine sites

Covalent small molecule probes are valuable tools for the global investigation of protein function. A large fraction of the human proteome remains undruggable, despite efforts to expand coverage of residues accessible by activity-based probes (serine, cysteine, lysine). In order to access this undruggable proteome, new chemistry must be introduced to access additional nucleophilic amino acid residues. This dissertation presents work in the development of sulfur-triazole exchange (SuTEx) chemistry as a new electrophile for chemical biology and protein ligand discovery.
Chapter 1 will present relevant background information on the advancement of chemo-proteomics and its application in ascribing protein function and drug discovery. The work presented in Chapter 2 details the initial development of the SuTEx platform and how modifications to the probe provided enhanced chemoselectivity for tyrosine over other nucleophilic amino acid residues, which enabled investigation of more than 10,000 tyrosine sites in lysates and in live cells. Further, we show the application of SuTEx as a chemical phosphoproteomics strategy to monitor the activation of phosphotyrosine sites. Chapter 3 focuses on development of a SuTEx fragment compound library to explore how modifications to the adduct group and leaving group affect reactivity for developing ligands to perturb protein function both in vitro and in live cells. Chapter 4 greatly expands on the SuTEx fragment ligand library to identify new lead compounds for optimization against select protein targets. Chapter 5 presents progress towards cysteine-reactive activity-based probes and small molecule tools to study and pharmacologically target lipid kinases. Diacylglycerol kinases (DGKs) represent an important class of lipid kinases that serve as key signaling mediators in lipid signaling pathways. This enzyme class is still ill-defined due to the high degree of difficulty in establishing selective tools to elucidate enzyme substrates and identify ligand binding regions for the chemical perturbation of protein function. Chapter 6 offers conclusions that have been made based upon the current work as well as provide additional future directions than those offered in Chapter 4. All available characterization data for SuTEx compounds can be found in the Appendix.