Attenuation control of pyrBI operon expression in Escherichia coli K-12.

• DOI: 10.1073/pnas.80.2.368
• Publication Date: 2006-05-31T09:14:10Z
• Authors: C L Turnbough; K L Hicks; J P Donahue
• Keywords: Aspartate carbamoyltransferase; Transcription; Attenuator (electronics); Terminator (solar); gal operon; L-arabinose operon; trp operon

The pyrBI operon of Escherichia coli K-12 encodes the subunits pyrimidine biosynthetic enzyme aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2). Expression this apparently is negatively regulated by intracellular levels UTP. To elucidate regulatory mechanism in which UTP functions, nucleotide sequence promoter-regulatory region was determined and DNA fragments containing were transcribed vitro. These experiments revealed a rho-independent transcriptional terminator (attenuator) located only 23 base pairs before promoter-proximal end structural genes. Transcription initiated upstream at either two potential promoters efficiently (approximately equal to 98%) terminated site, indicating that regulation expression involves attenuation control. Additional features identified suggest model for relative rates UTP-dependent transcription within leader coupled translation transcript control termination attenuator.