Article

Molecular and General Genetics MGG

, Volume 193, Issue 2, pp 244-250

First online:

Transcription of the trpR gene of Escherichia coli: An autogeneously regulated system studied by direct measurements of mRNA levels in vivo

  • Gregg BogosianAffiliated withDepartment of Biochemistry, Purdue University
  • , Ronald L. SomervilleAffiliated withDepartment of Biochemistry, Purdue University
  • , Kayoko NishiAffiliated withThe Institute of Physical and Chemical Research
  • , Yasunobu KanoAffiliated withThe Institute of Physical and Chemical Research
  • , Fumio ImamotoAffiliated withThe Institute of Physical and Chemical Research

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Summary

The expression of the trpR gene of Escherichia coli was investigated by measuring trpR messenger RNA levels in vivo under various physiological conditions. Trp repressor, when present, led to significant decreases in the amount of trpR message produced; this effect was enhanced by providing excess L-tryptophan to the system. In the absence of TrP repressor, no changes in trpR message levels were observed under any of the conditions employed. Sedimentation profiles of trpR mRNA revealed a single species under all circumstances. These results suggest that autogenous repression alone acts to regulate transcription of the trpR gene. The activity of the trpR promoter in vivo was evaluated using a trpR-lacZ operon fusion. Very good agreement was found between relative promoter activity and trpR message levels under all experimental conditions.