Discovery and characterization of biocatalysts and metabolites for ribosomally encoded alpha-N-methylated peptide natural products

University Of Minnesota, Minneapolis MN

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Abstract

PROJECT SUMMARY / ABSTRACT Since the discovery of penicillin in the 1920s, bioactive peptide natural products have been used as antibiotic, antiviral, immunosuppressive, and anti-cancer agents. Many of these bioactive peptides harbor backbone α-N-methylations and/or macrocyclizations, since these tailorings significantly improve peptide pharmacokinetics. As seen in the blockbuster immunosuppressant cyclosporin A, α-N-methylated peptides have increased structural rigidity, proteolytic resistance, and membrane permeability. Despite these advantages, inefficient synthetic and in vitro processes hinder the production, screening, and optimization of α-N-methylated peptides. In addition, natural sources of amide backbone-methylated peptides were thought to be completely limited to inflexible nonribosomal peptide biosynthetic pathways. The goal of this work is to identify new α-N- methylated metabolites and tease out the mechanistic and structural constraints of biocatalysts from our newly discovered ribosomally encoded peptide natural product family named the borosins. Our first objective aims to uncover rules of iterative catalysis, inhibition, and cooperativity in our model borosin system. Our second objective targets the discovery and study of structurally complex borosin metabolites from cystic fibrosis pathogens. Our last objective focuses on the mechanism and structure of α-N-methylation–dependent proteases and macrocyclases. This research will create a diverse toolbox of flexible and efficient catalysts for the biological production, screening, and optimization of genetically templated bioactive α-N-methylated peptides.