Phosphorylation of Ribosome-Associated Protein by an Adenosine 3′:5′-Cyclic Monophosphate-Dependent Protein Kinase: Location of the Microsomal Receptor and Protein Kinase

Abstract

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 NH₄Cl retain the substrate of the protein kinase reaction, but are dependent on the NH₄Cl 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.