Heterologous expression of the lanthipeptide mersacidin in Escherichia coli: biosynthesis, processing and engineering

The emergence of antimicrobial resistance against current antibiotics calls for new methods to obtain novel antimicrobial compounds. The lanthipeptide mersacidin, a short modified protein with antimicrobial activity, offers potential for this cause. While lanthipeptides are usually not suitable for direct use in the clinic, they can be improved by synthetic biology methods. Mersacidin has interesting intramolecular structures that can potentially be applied to obtain novel antimicrobials, as well as improved pharmaceuticals in general. In this thesis, a system is developed in which mersacidin can be expressed in the model organism Escherichia coli. Concurrently, the system was applied to gather knowledge on mersacidin biosynthesis and processing through genetic engineering. The results from this thesis supplement already existing knowledge, leading to the elucidation and understanding of the full mersacidin biosynthesis process. For this, crucial residues of the elusive leader peptide of mersacidin were identified through mutational analysis. Finally, it was found that the interesting intramolecular structures of mersacidin can indeed be produced in isolated form, making the future application of these structures a promising prospect. The results from this thesis can be used to continue research into the stabilization of pharmaceutical peptides, and the creation of novel antimicrobial peptides.