Role of the receptor in the mechanism of action of adenosine 3':5'-cyclic monophosphate.

Highly purified cAMP-dependent protein phosphokinase from adrenal-cortical tissue contains cAMP-receptor activity. In activating the kinase, cAMP binds to the receptor and causes it to dissociate from its complex with the kinase. The kinase, freed of receptor, is fully activated and no longer stimulable by cAMP. Kinase can be similarly activated by differentially denaturing the receptor with heat. Addition of receptor suppresses kinase activity; this suppression can be overcome by cAMP. After dissociation of receptor, two molecular forms of the activated kinase exist. The cAMP receptor thus functions as a repressor of the protein kinase; binding of cAMP to receptor causes it to dissociate from the kinase, which is then fully activated.