Leveraging Organophosphorus Chalcogen Reactivity in the Study of Post-Translational Protein Modifications

Abstract

The Human Genome Project uncovered the intricacy of the genetic code that governs life and raised an interesting evolutionary question; with just shy of 20,000 protein-encoding genes, why does the human genome contain far fewer genes than originally expected? One widely accepted and thoroughly studied explanation is through post-translational modification (PTM) of proteins. Following ribosomal translation, proteins are subject to a myriad of covalent processing events, enacted by enzymatic machinery to install or remove chemical functionality with remarkable efficiency and exquisite selectivity. The diversity of this chemical functionality is matched only by the complex impact on downstream physiological function. This has led to extensive investigation into PTMs in an attempt to understand the staggering complexity of the molecular cell, focusing on reliable methods for accessing proteins bearing native PTMs or non-native modifications outside of Nature’s repertoire. This thesis describes developments in chemical methodology to enable the study of the role of PTMs in proteins and explore the potential of modified peptides and proteins as therapeutic agents. Chapter 1 introduces the structurally and functionally diverse collection of post-translational protein modifications and details the chemical and biological methods to modify peptide and protein molecules to better understand their physiological function. Chapter 2 describes the development of a bioconjugation platform leveraging highly efficient reactivity between organophosphorus reagents and selenoproteins in the aim of studying the therapeutic potential of modified proteins. Chapter 3 entails the use of organophosphorus reactivity at cysteine to enable investigation of the role of native PTMs via isosteric mimicry. Chapter 4 describes studies towards the development of anti-SARS-CoV-2 therapeutics via de novo discovery of modified bioactive peptides using the RaPID mRNA display platform.