EXPLORING THE THERAPEUTIC POTENTIAL OF POST- TRANSLATIONALLY MODIFIED PEPTIDES AND PROTEINS

Abstract

The human genome encodes ~20,000 different primary sequences of proteins, far too few to account for the staggering complexity exhibited by mammalian life. Indeed, it is the exponential expansion of these ~20,000 biomolecules via self-modification that explains how proteins are able to orchestrate the intricacies of human biology. These modification events, termed ‘post-translational modifications’ (PTMs), vary in their structure; from the small addition of a -CH3 in lysine methylation to the addition of a whole other protein in ubiquitination. In endogenous systems, PTMs play a crucial role in modulating the activity of proteins, particularly in enhancing the affinity of protein-protein interactions (PPIs).

Despite their essential role in regulating the activity of endogenous biomolecules, the utility of PTMs in improving the efficacy of peptide and protein drugs remains an underexplored area. This thesis details the investigation of PTMs as a means to enhance the biological activity of peptides and proteins. These modified biomolecules were then profiled as therapeutic leads for several prominent diseases, namely sepsis, thromboembolic disorders and SARS-CoV-2 infection. To this end, Chapter 2 details the incorporation of the tyrosine sulfate PTM into mRNA display to target C5a, a protein strongly implicated in sepsis mortality. Chapter 3 and 4 describe the profiling of both native sulfoproteins and the de novo engineering of peptides bearing this PTM to inhibit thrombin, the key enzyme that potentiates thromboembolism. Finally, Chapter 5 investigates the incorporation of a bacterial lipidation motif that is recognised by the immune system to enhance the activity of intranasal SARS-CoV-2 vaccines.