A global transcription regulator required for bacterial competence. Complexes with cyclic AMP (cAMP) which allosterically activates DNA binding (to consensus sequence 5'-AAATGTGATCTAGATCACATTT-3') to regulate transcription at 54 promoters (PubMed:15769466). There are 2 consensus subclasses; CRP-N (above) and CRP-S (T6 changed to C and A17 changed to G) which obligatorily also requires Sxy for expression. CRP-S sites bind DNA but do not activate transcription in the absence of Sxy. Probably induces a severe bend in DNA. Probably acts as a negative regulator of its own synthesis as well as for adenylate cyclase (cyaA), which generates cAMP. Homodimer, which upon binding cAMP is able to bind DNA (Probable). Binds RNA polymerase subunit RpoA (By similarity). Constitutively expressed; slightly induced on shifting to starvation media. The N-terminal domain binds cAMP and is responsible for homodimerization, while the C-terminal domain binds DNA when cAMP is bound. Loss of competence, the ability to bind, take-up and integrate exogenous DNA. Loss of the ability to ferment ribose or xylose.