A global transcription regulator. Complexes with cyclic AMP (cAMP) which allosterically activates DNA binding to regulate transcription. It can act as an activator, repressor, coactivator or corepressor. Induces a severe bend in DNA. Acts as a negative regulator of its own synthesis as well as for adenylate cyclase (cyaA), which generates cAMP. Plays a major role in carbon catabolite repression (CCR) (By similarity). Homodimer, which upon binding cAMP is able to bind DNA. Binds the N- and C-terminus of RNA polymerase subunit RpoA and sigma-70 (RpoD) (By similarity). The N-terminal domain binds cAMP and is responsible for homodimerization, while the C-terminal domain binds DNA when cAMP is bound.