cAMP receptor protein (CRP; also known as catabolite activator protein, CAP) is a

regulatory protein Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are wide ...

in bacteria. CRP protein binds cAMP, which causes a conformational change that allows CRP to bind tightly to a specific DNA site in the promoters of the genes it controls. CRP then activates transcription through direct protein–protein interactions with

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

. The genes regulated by CRP are mostly involved in energy metabolism, such as galactose, citrate, or the PEP group translocation system. In '' Escherichia coli'', cyclic AMP receptor protein (CRP) can regulate the transcription of more than 100 genes. The signal to activate CRP is the binding of cyclic AMP. Binding of cAMP to CRP leads to a long-distance signal transduction from the N-terminal cAMP-binding domain to the C-terminal domain of the protein, which is responsible for interaction with specific sequences of DNA. At "Class I" CRP-dependent promoters, CRP binds to a DNA site located upstream of core promoter elements and activates transcription through protein–protein interactions between "activating region 1" of CRP and the C-terminal domain of

alpha subunit. At "Class II" CRP-dependent promoters, CRP binds to a DNA site that overlaps the promoter -35 element and activates transcription through two sets of protein–protein interactions: (1) an interaction between "activating region 1" of CRP and the C-terminal domain of

alpha subunit, and (2) an interaction between "activating region 2" of CRP and the N-terminal domain of

alpha subunit. At "Class III" CRP-dependent promoters, CRP functions together with one or more " co-activator" proteins. At most CRP-dependent promoters, CRP activates transcription primarily or exclusively through a "recruitment" mechanism, in which protein–protein interactions between CRP and

assist binding of

to the promoter.

References

{{DEFAULTSORT:cAMP Receptor Protein Bacterial proteins