The lac operon of the Escherichia coli bacterium - Positive transcriptional control of the lac operon by the polymerase transactivator protein cAMP-CAP.

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The lac operon of the Escherichia coli bacterium - Positive transcriptional control of the lac operon by the polymerase transactivator protein cAMP-CAP - Animation©E.Schmid/SWC2002

Scenario 1  both, glucose and lactose, are available for the cell

lacIPOlacZlacYlacA lac operon no transcription ! Glucose + Lactose + Escherichia coli (E.coli) RNApolymeraseRepressor Glucose metabolism

lacIPOlacZlacYlacA no transcription ! Glucose + Lactose + Escherichia coli (E.coli) Lactose binding & Conformational change Porin

lacIPOlacZlacYlacA low transcription rate Glucose + Lactose + Escherichia coli (E.coli) Dissociation of lac repressor

Scenario 2  glucose level drops  no glucose for metabolism available

lacIPOlacZlacYlacA low transcription rate! Low glucose Lactose + + glucose sensor

lacIPOlacZlacYlacA low transcription rate! no glucose Lactose + + Adenylatecyclase

lacIPOlacZlacYlacA low transcription rate! no glucose Lactose + ATP cAMP

lacIPOlacZlacYlacA low transcription rate! no glucose Lactose + cAMP binding + cAMP-CAP

lacIPOlacZlacYlacA low transcription rate! no glucose Lactose + cAMP DNA binding

lacIPOlacZlacYlacA high transcription rate! no glucose Lactose + cAMP POL transactivation +

lacIPOlacZlacYlacA high transcription rate! no glucose Lactose + cAMP mRNA

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