Biochemical characterization of enzymes involved in the biosynthesis of the thiopeptide thiomuracin
Clinically significant antibiotic resistance has evolved against virtually every antibiotic currently deployed, therefore it is critical for human health to discover new antibacterial agents with novel modes of action. Thiopeptides are a family of ribosomally synthesized and post-translationally modified peptides (RiPPs) that have outstanding biological profile, including high potency against a variety of antibiotic resistant pathogenic strains. Their new modes of action have attracted many efforts to develop chemical syntheses, and to study their biological function and biosynthetic origin. However, the complex architecture and poor physicochemical properties have plagued this otherwise-promising class of antibiotics. To address these challenges, this dissertation used the thiopeptide thiomuracin as a model to establish the reconstitution of the biosynthesis of thiopeptide in vitro, and to characterize the activity of the highly unusual modification enzymes involved in thiopeptide biosynthetic pathway. This work will guide future efforts to improve the properties of thiopeptide natural products. The biosynthesis of the thiopeptide thiomuracin is a well-orchestrated process involving a multitude of post-translational modifications. Chapter 2 presents the first in vitro biosynthesis of the core scaffold of thiopeptide thiomuracin, while Chapter 3 will provide insights into the substrate specificities, directionality, and timing of catalysis by six proteins involved in the formation of this core scaffold of thiopeptides. Characterization and mechanistic investigation of TbtI, a radical S-adenosyl-L-methionine thiazole C-methyltransferase involved in the tailoring modification of thiomuracin, are presented in Chapter 4. Lastly, Chapter 5 discusses the characterization of an ATP and tRNA dependent peptidyl transferase involved in a pathway where a ribosomally synthesized small peptide serves as a catalytic scaffold on which a small-molecule is biosynthesized in Pseudomonas syringae.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign