PMID: 8468295Apr 1, 1993Paper

Genetic evidence that promoter P2 is the physiologically significant promoter for the pyrBI operon of Escherichia coli K-12

Journal of Bacteriology
C LiuC L Turnbough

Abstract

The pyrBI operon of Escherichia coli K-12 encodes the two nonidentical subunits of the pyrimidine biosynthetic enzyme aspartate transcarbamylase (ATCase). Expression of this operon is negatively regulated by pyrimidine availability primarily through UTP-sensitive transcriptional attenuation and, to a lesser extent, at the level of transcriptional initiation. Previous studies indicated that the pyrBI operon was transcribed from tandem sigma 70 promoters designated P1 and P2, with the large majority of transcription initiated at the more downstream promoter P2. To more clearly define the roles of these promoters, mutations that severely impair or inactivate individual promoters were constructed in the chromosomal pyrBI operon, and their effects on ATCase synthesis were measured. In cells grown under conditions of either pyrimidine excess or pyrimidine limitation, more than 99% of all ATCase synthesis was directed by transcripts initiated at promoter P2, indicating that it is the only physiologically significant pyrBI promoter. However, mutations that effectively inactivate promoter P1 caused a 15% reduction in ATCase levels, apparently by inhibiting transcription from promoter P2 by an unknown mechanism. Support for this explanat...Continue Reading

References

Dec 1, 1977·Proceedings of the National Academy of Sciences of the United States of America·F SangerA R Coulson
Mar 1, 1991·Journal of Bacteriology·H MoyleM M Susskind
Oct 1, 1988·Proceedings of the National Academy of Sciences of the United States of America·K L RolandC L Turnbough
Jan 1, 1989·Proceedings of the National Academy of Sciences of the United States of America·J R WildT S Corder
Jul 1, 1987·European Journal of Biochemistry·G MichaelsF E Nargang
Mar 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·M Navre, H K Schachman
Jan 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·C L TurnboughJ P Donahue
Jan 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·H K SchachmanY R Yang

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