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A previously undescribed pathway for pyrimidine catabolism
Kevin D Loh1, Prasad Gyaneshwar, Eirene Markenscoff Papadimitriou
1Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA.
Summary
The b1012 operon in Escherichia coli facilitates pyrimidine utilization, converting uridine and thymidine into 3-hydroxypropionic acid. This pathway is regulated by the b1013 gene product.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- The b1012 operon in Escherichia coli K-12 is highly expressed under nitrogen regulatory protein C control.
- Its function in nutrient utilization was previously unidentified.
Purpose of the Study:
- To elucidate the function of the b1012 operon in Escherichia coli.
- To identify the metabolic products and regulatory mechanisms involved in pyrimidine utilization.
Main Methods:
- Phenotype MicroArray analysis (PM3) and growth tests were used to assess nutrient utilization.
- Radioisotope labeling with [(14)C]uridine and mass spectrometry identified metabolic byproducts.
- Gas chromatography was employed for waste product analysis.
Main Results:
- Escherichia coli strains with lesions in the b1012 operon could not utilize uridine or uracil as a nitrogen source.
- The operon is responsible for the catabolism of pyrimidines, producing 3-hydroxypropionic acid from uridine and 2-methyl-3-hydroxypropionic acid from thymidine.
- A regulator encoded by b1013 negatively controls the transcription of the b1012 operon.
Conclusions:
- The b1012 operon (proposed name rutA-G) encodes a novel pathway for pyrimidine utilization in Escherichia coli.
- This pathway differs from previously described pyrimidine catabolic pathways in its nitrogen availability and waste products.
- Pyrimidine catabolism is regulated by the b1013 gene product, a tetracycline repressor family regulator.