Open AccessInteraction of the Subunits of Adenosine 3′:5′-Cyclic Monophosphate-Dependent Protein Kinase of Muscle
Author(s) -
Charles O. Brostrom,
Jackie D. Corbin,
Carol A. King,
Edwin G. Krebs
Publication year - 1971
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.68.10.2444
Subject(s) - protein subunit , gi alpha subunit , protein kinase a , phosphodiesterase 3 , pde10a , biochemistry , enzyme , kinase , phosphodiesterase , adenosine , intracellular , cyclic adenosine monophosphate , chemistry , biology , receptor , gene
Two cAMP-dependent protein kinases purified from rabbit skeletal muscle were shown to bind the same amount of cAMP per unit of enzyme activity at several concentrations of this nucleotide. A preparation containing both of these kinases was separated into catalytic (C) and regulatory (R) subunit fractions in the presence of cAMP, the regulatory subunit being obtained as an R·cAMP complex. Addition of increasing amounts of the R·cAMP complex to the holoenzyme (RC) increased the concentration of cAMP required for half-maximal activity of the enzyme. cAMP was liberated from the R·cAMP complex in the presence of added catalytic subunit in a reaction that was facilitated by Mg2+ , ATP, and warming. These findings are presented in support of a model for activation of the protein kinase by cAMP. The possibility that excess regulatory subunit may serve as a sink for intracellular cAMP is also discussed. It is shown that cAMP bound to the R subunit is not a substrate for the cAMP phosphodiesterase.