From: How Genetic Switches Work
Copyright © 1994, Bruce Alberts, Dennis Bray, Julian
Lewis, Martin Raff, Keith Roberts, and James D Watson.
NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.
Alberts B, Bray D, Lewis J, et al. Molecular Biology of the Cell. 3rd edition. New York: Garland Science; 1994.
Molecular Biology of the Cell. 3rd edition.
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Figure 9-29Dual control of the lac operon
Glucose and lactose levels control the initiation of transcription of the lac operon through their effects on the lac repressor protein and CAP. Lactose addition increases the concentration of allolactose, which binds to the repressor protein and removes it from the DNA. Glucose addition decreases the concentration of cyclic AMP; because cyclic AMP no longer binds to CAP, this gene activator protein dissociates from the DNA, turning off the operon. As shown in Figure9-8, CAP is known to induce a bend in the DNA when it binds; for simplicity, the bend is not shown here. LacZ,the first gene of the lac operon, encodes the enzyme β-galactosidase, which breaks down lactose to galactose and glucose.
- Figure 9-29, Dual control of the lac operon - Molecular Biology of the CellFigure 9-29, Dual control of the lac operon - Molecular Biology of the Cell
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