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Enzymatic Thioamide Formation in a Bacterial Antimetabolite Pathway
Agnieszka Litomska1, Keishi Ishida1, Kyle L Dunbar1
1Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Chemistry and Infection Biology (HKI), Beutenbergstr. 11a, 07745, Jena, Germany.
Researchers discovered a unique enzyme system in plant pathogens that creates 6-thioguanine (6TG), a cancer drug and bacterial toxin. This finding reveals novel mechanisms for forming carbon-sulfur bonds in nature.
Area of Science:
- Biochemistry
- Natural Product Biosynthesis
- Enzymology
Background:
- 6-Thioguanine (6TG) is a DNA-targeting anticancer drug and a virulence factor in plant pathogens Erwinia amylovorans.
- Its biosynthesis involves a rare oxygen-by-sulfur substitution, the mechanism of which was previously unknown.
Purpose of the Study:
- To elucidate the enzymatic machinery responsible for 6TG biosynthesis.
- To understand the evolutionary origins and biochemical mechanisms of this unique thioamidation process.
Main Methods:
- Gene expression analysis
- Biochemical assays
- Mutational analyses
- Mechanistic and phylogenetic studies
- In vitro reconstitution of 6TG thioamidation
Main Results:
- Identified a bipartite enzyme system (YcfA and YcfC) responsible for the oxygen-by-sulfur substitution in 6TG biosynthesis.
- Demonstrated that YcfA-mediated 6TG biosynthesis evolved from ancient tRNA modifications.
- Showcased YcfA's specialized sulfur shuttle distinct from universal RNA-related systems.
Conclusions:
- The study reveals a novel enzymatic pathway for C-S bond formation in natural product biosynthesis.
- This work sheds light on the evolution of enzymes involved in both natural product synthesis and essential cellular processes like translation.
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