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Mutants with substitutions for Glu171 in the catabolite activator protein (CAP) of Escherichia coli activate transcription from the lac promoter (1993)

Breul, Astrid ; Aßmann, Heike ; Golz, Regina ; [et al.]

Springer

Molecular genetics and genomics 238 (1993), S. 155-160

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ISSN: 1617-4623

Keywords: Catabolite activator protein (CAP) ; Transcription activator ; Protein-protein interaction ; Positive control mutants ; DNA-binding protein

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Single amino acid substitutions for residue Glu171 in helix E of the catabolite gene activator protein (CAP) of Escherichia coli have been reported to abolish activation of transcription without impairing binding to the CAP site of the lac promoter. The negative charge of Glu171 was proposed to transmit the activating signal from CAP to RNA polymerase. However, this idea has been challenged by later work. We set up a system to re-examine this issue. We analysed the ability of mutant CAP-E 171 L and CAP-E 171 K proteins to bind a nearconsensus CAP site in vivo and found it to be diminished fourfold relative to wild type in each case. Activation of lac transcription by these mutant proteins remains the same as with wild-type CAP. Thus our results confirm that Glu171 in helix E of CAP is not involved directly in the activation of transcription. Yet CAP-E171K does not activate transcription as well as wild-type CAP under all circumstances. Possible reasons for this absence of activation are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00279542

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Electronic Resource

Lac Repressor (1971)

Müller-Hill, Benno

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 10 (1971), S. 160-172

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ISSN: 0570-0833

Keywords: Lac repressor ; Repressors ; Proteins ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Repressors are proteins that interact with inducers and operators to regulate the synthesis of enzymes in the cell. Lac repressor ensures that sufficient β-galactosidase is available to the bacterium Escherichia coli, depending upon the amount of lactose present in the culture medium. It has proved possible to isolate lac repressor from E.coli. The present progress report describes how these discoveries were made, as well as the formation and mode of action of the repressor.

Additional Material: 8 Ill.