In Dictyostelium the holoenzyme is a dimer composed of a regulatory (R) and a catalytic (C) subunit. In the presence of cAMP it dissociates into the active C subunit and an R monomer. In other eukaryotes the holoenzyme is a tetramer composed of 2 regulatory (R) and 2 catalytic (C) subunits. In the presence of cAMP it dissociates into active monomeric C subunits and an R dimer. Lacks the N-terminal domain required for the association of regulatory subunits into dimers in other eukaryotes. 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. AcaA and pkaR double mutant shows no abolition of the ability to sporulate. In D.discoideum each R subunit carries only 1 high-affinity cAMP binding site (2 in other eukaryotes). Belongs to the cAMP-dependent kinase regulatory chain family.