Tags: Protein.
Proteins that bind cyclic nucleotides (cAMP or cGMP) share a structural domain of about 120 residues. The best studied of these proteins is the prokaryotic catabolite gene activator (also known as the cAMP receptor protein) (gene crp) where such a domain is known to be composed of three alpha-helices and a distinctive eight-stranded antiparallel beta-barrel structure.