title: Formation of inactive cAMP-saturated holoenzyme of cAMP-dependent protein kinase under physiological conditions.
abstract: The complex of the subunits (RIalpha, Calpha) of cAMP-dependent protein kinase I (cA-PKI) was much more stable (K(d) = 0.25 microm) in the presence of excess cAMP than previously thought. The ternary complex of C subunit with cAMP-saturated RIalpha or RIIalpha was devoid of catalytic activity against either peptide or physiological protein substrates. The ternary complex was destabilized by protein kinase substrate. Extrapolation from the in vitro data suggested about one-fourth of the C subunit to be in ternary complex in maximally cAMP-stimulated cells. Cells overexpressing either RIalpha or RIIalpha showed decreased CRE-dependent gene induction in response to maximal cAMP stimulation. This could be explained by enhanced ternary complex formation. Modulation of ternary complex formation by the level of R subunit may represent a novel way of regulating the cAMP kinase activity in maximally cAMP-stimulated cells.
authors.affiliation: Department of Anatomy and Cell Biology, University of Bergen, N-5009 Bergen, Norway.
authors.forename: Reidun
authors.initials: R
authors.lastname: Kopperud
authors.forename: Anne Elisabeth
authors.initials: AE
authors.lastname: Christensen
authors.forename: Endre
authors.initials: E
authors.lastname: Kjarland
authors.forename: Kristin
authors.initials: K
authors.lastname: Viste
authors.forename: Hans
authors.initials: H
authors.lastname: Kleivdal
authors.forename: Stein Ove
authors.initials: SO
authors.lastname: Døskeland
mesh_terms: D002384:Catalysis; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009842:Oligopeptides / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014162:Transfection
chemical_list: D009842:Oligopeptides; C037642:kemptide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases