Elucidating the biosynthesis and function of oxazolones in Mycobacterium tuberculosis

• Applicant: Dr. Julia Kleetz
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 515015803

Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis (TB), caused more deaths last year than any other bacterial pathogen. A further ~25% of the world's population carry the bacterium as an asymptomatic, latent infection. Novel therapeutics are urgently needed, particularly in light of the rise of drug-resistant strains and the toxicity of current treatments. Mtb’s success as a pathogen is in part due to its sophisticated program for lipid metabolism, both catabolic and biosynthetic. Mtb synthesizes a range of unusual lipids, some of which have roles in pathogenicity and persistence. Nevertheless, the identity and roles of many of these lipids are unknown. The research group that will host my postdoctoral studies recently discovered two gene clusters in Mtb that encode the biosynthesis of different acylated oxazolones: Rv1356c-Rv1355c and Rv2336-Rv2337c-Rv2338c encode the biosynthesis of valeryl-tryptazolone (C5-tryptazolone) and lauroyl-tyrazolone (C12-tyrazolone), respectively. Acylated oxazolones are an unusual, poorly characterized class of lipids, although the genes involved in the biosynthesis of C12-tyrazolone are predicted to be important for Mtb’s pathogenesis, and one of its biosynthetic enzymes has been proposed to be a target of a potent anti-TB compound. The genes of the two clusters encode three enzyme activities: an acyltransferase that catalyzes the N-acylation of an aromatic L-amino acid; a flavin-dependent oxidase (FDO) that catalyzes a desaturation; and a ThiF that catalyzes the cyclization of the N-acyl amino acid to yield the oxazolone. In the Rv1356c-Rv1355c cluster, ThiF-FDO occurs as a fusion protein. The overall objective of the project aims to elucidate the biosynthesis and function of the oxazolones. The specific aims are: (1) to characterize the biosynthetic enzymes; (2) to determine the physiological role of oxazolones; and (3) to evaluate the potential of the enzymes as therapeutic targets. These aims will be achieved using a multidisciplinary approach drawn from biochemistry, enzymology, molecular genetics, microbiology, structural biology, and metabolomics. Improved understanding of the biosynthetic enzymes, the oxazolones, and their role in pathogenesis will facilitate the development of novel therapeutics. In addition, the proposed research will greatly increase our understanding of a novel class of lipids as well as of several enzyme superfamilies.

• DFG Programme: WBP Fellowship
• International Connection: Canada
• Host: Professor Lindsay Eltis, Ph.D.