The inactive form of the enzyme is composed of two regulatory chains and two catalytic chains. Activation by cAMP produces two active catalytic monomers and a regulatory dimer that binds four cAMP molecules. The pseudophosphorylation site binds to the substrate-binding region of the catalytic chain but is not phosphorylated. The physiological significance of phosphorylations by other kinases is unclear. Belongs to the cAMP-dependent kinase regulatory chain family.