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Pathway Description
Operon: Pyrimidine Biosynthesis Inactivation
Escherichia coli
Signaling Pathway
The pyrimidine biosynthesis operon consists of the genes pyrB and pyrI. This is a bicistronic operon. The operon transcription is negatively regulated by the intracellular levels of UTP. The higher the UTP levels, the less expression of the operon. High concentrations of UTP indicate sufficient pyrimidine levels hence UTP binds to the regulatory subunit of ATCase ( catalyzes the first committed step in pyrimidine biosynthesis), resulting in a conformational change and reduced activity. High UTP levels also repress the transcription of this operon through the pyrl regulatory protein, which binds to the promoter region of the pyr operon, preventing RNA polymerase from binding and initiating transcription.
References
Operon: Pyrimidine Biosynthesis Inactivation References
Turnbough CL Jr, Hicks KL, Donahue JP: Attenuation control of pyrBI operon expression in Escherichia coli K-12. Proc Natl Acad Sci U S A. 1983 Jan;80(2):368-72.
Pubmed: 6300835
Wild, J.R., Loughrey-Chen, S.J. and Corder, T.S., 1989. In the presence of CTP, UTP becomes an allosteric inhibitor of aspartate transcarbamoylase. Proceedings of the National Academy of Sciences, 86(1), pp.46-50.
Turnbough Jr, C.L., Hicks, K.L. and Donahue, J.P., 1983. Attenuation control of pyrBI operon expression in Escherichia coli K-12. Proceedings of the National Academy of Sciences, 80(2), pp.368-372.
Turnbough Jr, C.L. and Switzer, R.L., 2008. Regulation of pyrimidine biosynthetic gene expression in bacteria: repression without repressors. Microbiology and Molecular Biology Reviews, 72(2), pp.266-300.
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