Catabolite gene activator protein (CAP) is a DNA-binding protein involved in the transcription of several genes including those involved in the metabolism of sugar. CAP can activate or repress transcription initiation upon binding of cAMP. The cAMP-CAP complex binds to promoters on the DNA. The structure contains a ligand-binding domain (LBD) at the N-terminal and DNA-binding domain (DBD) at the C-terminal. Two cAMP molecules bind to the dimeric CAP. When the amount of glucose transported into the cell is low, cAMP level rises and the cAMP-CAP complex causes increase of transcription of glucose metabolism genes.
