Metal-mediated Ligand Affinity Chemistry

PROJECT SUMMARY/ABSTRACT. Chemical reagents for modification of peptides and proteins have led to a wide variety of peptide and protein conjugates to study protein function and as therapeutics. Despite the advancement, inherent limitations of current methods make new chemical tools a necessity for protein chemical modification and biomolecule manipulation particularly within their native sites in vitro or in vivo. Specifically, small-molecule drugs containing reactive warheads irreversibly modify endogenous proteins for therapeutic gain as evidenced in the proteasome inhibitor, bortezimib and tyrosine kinase inhibitors, e.g. ibrutinib. These developments have generated excitement in the field of small-molecule covalent modifiers. Recent chemistry examples applied to peptides and proteins involve the use of organic and inorganic tools to covalently modify proteins for labeling, structure-function studies, and biotherapeutics including protein drugs and antibody-drug-conjugates. Currently, significant efforts are underway to design site-selective chemical conjugation of synthetic molecules to expand the functional and therapeutic capacity of proteins. The chemical modification of natural amino acids in peptides and proteins including protein-protein interactions (PPIs) has proved challenging due to the use of a bioorthogonally-labeled partner restricted to the N- or C-terminus or the need for extensive sequence engineering. Importantly, the reactions employed in site-selective protein conjugation need to be chemoselective, regioselective, and operational under mild, physiologically relevant conditions. Here, we propose to develop metal-mediated cysteine and lysine arylation as an elaborate tool for bioconjugation, explore extensive structure-function relationship studies on select peptides and proteins and to decipher intracellular target potential of this arylation strategy. The aims of the proposed work are: Aim 1) investigate cysteine/lysine arylation with gold-based reagents; Aim 2) carry out structure-function studies on proteins and explore lysine reactivity and ligandability within the human proteome; and Aim 3) determine the intracellular target modulation of proteins by gold- based reagents. In summary, we posit that the studies delineated here will provide critical solutions to longstanding problems in chemical biology by introducing an innovative method to selectively modify peptides and proteins.