Sulfotyrosine-Containing Plant Peptide Hormones: Synthetic Approaches and Nanopore Sequencing of Post-Translationally Modified Peptides

Summary

Post-Translational Modifications (PTMs) are essential for protein structure and function. While phosphorylation (PO3H2) is a common PTM on natural proteins to regulate intracellular signaling, sulfation (SO3H) is found important for plant growth and development. Plant Peptide Hormones (PPHs) are naturally occurring regulatory molecules that are bio-active at nanomolar concentrations. Three PTMs are identified in PPHs, namely: sulfotyrosine, hydroxyproline, and triarabinosylated hydroxyproline. While in vivo modification of PTMs occurs enzymatically, the chemical synthesis of sulfotyrosine-containing peptides is compromised by the acid-labile character of the sulfate group. Moreover, identification or analysis of sulfo-containing peptides or proteins is still difficult using standard mass spectrometric methods.
In this Thesis, the chemical synthesis of two types of sulfotyrosine-containing PPHs is described, followed by their evaluation of biological activity in a protoplast proliferation assay. Then, PTM identification and peptide analysis by means of nanopore sequencing is developed to enable further protein analysis.