Catabolite activator protein

[3] CAP's name is derived from its ability to affect transcription of genes involved in many catabolic pathways.

For example, when the amount of glucose transported into the cell is low, a cascade of events results in the increase of cytosolic cAMP levels.

This increase in cAMP levels is sensed by CAP, which goes on to activate the transcription of many other catabolic genes.

CAP has a characteristic helix-turn-helix motif structure that allows it to bind to successive major grooves on DNA.

[4] This interaction opens up the DNA molecule, allowing RNA polymerase to bind and transcribe the genes involved in lactose catabolism.