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The regulatory subunit of the type I cAMP-dependent protein kinase (Rt) serves as a substrate for the phosphotransferase reaction catalyzed by cGMP-dependent protein kinase (Km = 2.2 microM). The reaction is stimulated by cGMP when RI . cAMP is the substrate, but not when nucleotide-free RI is used. The cGMP-dependent protein kinase catalyzes the incorporation of 2 mol of phosphate/mol of RI dimer in the presence of cAMP and a self-phosphorylation reaction to the extent of 4 mol of phosphate/mol of enzyme dimer. In the absence of cAMP, RI is a competitive inhibitor of the phosphorylation of histone H2B (Ki = 0.25 microM) and of the synthetic peptide substrate Leu-Arg-Arg-Ala-Ser-Leu-Gly (Ki = 0.15 microM) by the cGMP-dependent enzyme. Nucleotide-free RI also inhibits the intramolecular self-phosphorylation of cGMP-dependent protein kinase. The inhibition of the phosphorylation reactions are reversed by cAMP. The catalytic subunit of cAMP-dependent protein kinase does not catalyze the phosphorylation of RIand does not significantly alter the ability of RI to serve as a substrate or an inhibitor of cGMP-dependent protein kinase. These observations are consistent with the concept that the cGMP- and cAMP-dependent protein kinases are closely related proteins whose functional domains may interact.
R L Geahlen, and
E G Krebs
March 1986,
FEBS letters,
R L Geahlen, and
E G Krebs
June 1981,
The Journal of biological chemistry,
R L Geahlen, and
E G Krebs
November 1995,
FEBS letters,
R L Geahlen, and
E G Krebs
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Methods in enzymology,
R L Geahlen, and
E G Krebs
December 1979,
The Journal of biological chemistry,
R L Geahlen, and
E G Krebs
August 2002,
Trends in cardiovascular medicine,
R L Geahlen, and
E G Krebs
March 1991,
Biochemistry,
R L Geahlen, and
E G Krebs
August 1987,
FEBS letters,
R L Geahlen, and
E G Krebs
January 1988,
Methods in enzymology,
R L Geahlen, and
E G Krebs
August 1986,
The Journal of biological chemistry,
