1. Experiments were devised to show whether catabolite repression of β-galactosidase synthesis operates at the level of transcription or of translation. Escherichia coli K12 was induced for a short period in non-repressing medium (glycerol–minimal medium), and transcription of the lac operon was terminated by either of two methods; glucose was then added as a source of the catabolite repressor during the subsequent translation of the accumulated β-galactosidase messenger RNA. 2. When induced bacteria in glycerol medium were infected with T6 phage, which is known to halt transcription, the addition of glucose up to 3min. later diminished the yield of β-galactosidase. 3. When induced bacteria in glycerol medium were removed from the inducer and resuspended in fresh medium (a process that is also known to halt transcription), the yield of enzyme was again diminished by the presence of glucose in the resuspension medium. 4. It is concluded that repression of β-galactosidase synthesis can be brought about by the presence of glucose during the translation phase only. 5. In E. coli strain 300U the effect on translation was sufficient to account for almost all the catabolite repression of β-galactosidase synthesis observed during exponential growth of the organism in glucose–minimal medium. In E. coli strain 200P, however, much more severe repression occurred during exponential growth, and an additional effect of glucose is postulated.
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June 1969
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Research Article|
June 01 1969
Catabolite repression of the lac operon. Repression of translation
M D Yudkin;
M D Yudkin
1Microbiology Unit, Department of Biochemistry, University of Oxford
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V. Moses
V. Moses
1Microbiology Unit, Department of Biochemistry, University of Oxford
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Publisher: Portland Press Ltd
© 1969 The Biochemical Society
1969
Biochem J (1969) 113 (2): 423–428.
Citation
M D Yudkin, V. Moses; Catabolite repression of the lac operon. Repression of translation. Biochem J 1 June 1969; 113 (2): 423–428. doi: https://doi.org/10.1042/bj1130423
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