Phosphorylation of ribosome-associated protein by an adenosine 3':5'-cyclic monophosphate-dependent protein kinase: location of the microsomal receptor and protein kinase.

In the adrenal cortex, the adenosine 3':5'-cyclic monophosphate (cAMP)-receptor protein and the cAMP-dependent protein kinase are located in both the cytosol and endoplasmic reticulum. The cAMP-dependent protein kinase from the cytosol catalyzes the phosphorylation of ribosome-associated protein. Ribosomes washed in 0.5 M NH(4)Cl retain the substrate of the protein kinase reaction, but are dependent on the NH(4)Cl extract for in vitro protein synthesis. Dissociation of the 80S ribosomes by 0.88 M KCl, however, releases the ribosome-associated (protein) substrate of the phosphorylation reaction.