title: The function of Mg-ATP in interactions between the regulatory and catalytic subunits of type I cAMP-dependent protein kinase from rabbit skeletal muscle.
abstract: The regulatory subunit of Type I cAMP-dependent protein kinase from rabbit skeletal muscle can bind [3H]cAMP to form the R-[3H]cAMP complex, and the slow phase of the enhanced exchange of free cAMP with [3H]cAMP from the R-[3H]cAMP complexes was studied under various conditions using the equilibrium isotope exchange technique. Results indicate that Mg-ATP and the catalytic subunit are absolutely required for the enhanced exchange reaction to occur, but phosphorylation of the regulatory subunit by Mg-ATP does not play a determining role in the slow rate of the dissociation/association of the Type I protein-kinase in the presence of cAMP and the catalytic subunit. We interpret the role of Mg-ATP as being one in which it may provide the structural attributes required for formation of a stabilized transient state of the cAMP-regulatory subunit-catalytic subunit ternary complex, an obligatory intermediate involved in the dissociation/association of Type I cAMP-dependent protein kinase.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D009132:Muscles / Q000201:enzymology*; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D013329:Structure-Activity Relationship; D014316:Tritium
chemical_list: D046911:Macromolecular Substances; D014316:Tritium; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases