Formation of inactive cAMP-saturated holoenzyme of cAMP-dependent protein kinase under physiological conditions.
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.
Kopperud
Reidun
R
Department of Anatomy and Cell Biology, University of Bergen, N-5009 Bergen, Norway.
Christensen
Anne Elisabeth
AE
Kjarland
Endre
E
Viste
Kristin
K
Kleivdal
Hans
H
Døskeland
Stein Ove
SO
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
D009842:Oligopeptides; C037642:kemptide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases