The PKA complex is formed by the association of catalytic and regulatory subunits. The regulatory subunit has a modular organization composed of a flexible linker domain followed by two cAMP binding domains in tandem (see figure below). The activation of PKA by cAMP binding unleashes numerous allosteric events throughout the entire PKA complex, including ligand binding cooperativity between the cAMP binding domains, a dramatic conformational change in the regulatory subunit, and the dissociation of the complex into catalytic and regulatory subunits.