Abstract by Joshua McPhie
Chemistry and Biochemistry
Detection of Cysteine-to-Thiazole Modifications on Engineered Peptides
Post-translational modification (PTM) of polypeptide chains is essential for controlling protein activity in all life forms. In many families of antimicrobial peptides, PTMs are essential for their biological functions. We are studying the antimicrobial peptide TclE found in the organism Macrococcus caseolyticus. Six Cys residues near the C-terminal end of TclE are converted to thiazoles by the tripartite enzyme complex TclIJN. We are researching the mechanism for installation of these post-translational modifications. Our current hypothesis is that specificity for modification of individual cysteines, is driven by binding of the N-terminal half of the peptide to the TclIJN complex. To better describe this binding site on TclIJN, we co-expressed a GST-TclE fusion and the TclIJN enzyme in E. coli. After purification of TclE and removal of the GST purification tag, we used a targeted MS2 method on an LC-MS Orbitrap Mass Spectrometer to test the effect of truncations with various lengths. This research could lead to the generation of engineered thiazolyl peptides with novel biological activities.