Adenosine cyclic 3',5'-monophosphate dependent protein kinase: nucleotide binding to the chemically modified catalytic subunit.

5'-[p-(Fluorosulfonyl)benzoyl]adenosine (FSBA) inactivates the catalytic subunit of the adenosine cyclic 3',5'-monophosphate dependent protein kinase isolated from bovine cardiac muscle by covalent modification of lysine-71, whereas 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) react with cysteines-199 and -343 to inactivate the enzyme. All three of these reagents have been postulated to modify residues at or near the active site of the catalytic subunit. ATP (2 mM) in the presence of excess Mg2+ (10 mM) protects the enzyme against inactivation by these reagents. AMP did not afford any protection, but adenosine slightly decreased the rate of inactivation. The specific effects of covalent modification of lysine-71 and cysteines-199 and -343 on nucleotide binding were characterized by fluorescence-polarization titrations with lin-benzoadenine nucleotides as fluorescent ligands. lin-Benzoadenosine is a competitive inhibitor of the catalytic subunit with respect to ATP with a Ki (38 microM) similar to the Ki for adenosine (35 microM). This value agrees well with the Kd (32 microM) for adenosine determined by fluorescence-polarization titrations. lin-Benzoadenosine 5'-diphosphate (lin-benzo-ADP) has been shown to be a competitive inhibitor with respect to ATP [Hartl, F. T., Roskoski, R., Jr., Rosendahl, M. S., & Leonard, N. J. (1983) Biochemistry 22, 2347], and lin-benzoadenosine 5'-triphosphate (lin-benzo-ATP) is a substrate for the phosphotransferase activity of the protein kinase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine cyclic 3',5'-monophosphate dependent protein kinase: interaction of the catalytic subunit and holoenzyme with lin-benzoadenine nucleotides.

The interaction of lin-benzoadenosine di- and triphosphates with the catalytic subunit and type II holoenzymes of adenosine cyclic 3',5'-monophosphate (cAMP) dependent protein kinase has been investigated by steady-state kinetics and fluorescence spectroscopy. lin-Benzo-ADP is a competitive inhibitor of the catalytic subunit with respect to ATP with a Ki (8.0 microM) similar to the Ki for ADP (9.0 microM). This value agrees well with the Kd (9.0 microM) determined by fluorescence polarization titration. Type II holoenzymes from bovine brain and skeletal muscle have Kd values for lin-benzo-ADP of 3.4 microM and 3.5 microM, respectively, and each binds approximately 2 mol/mol of R2C2 tetramer. Furthermore, fluorescence polarization studies indicate that both the catalytic subunit and type II holoenzyme bind lin-benzo-ADP rigidly, so that there is little or no rotation of the lin-benzoadenine portion of the molecule within the nucleotide binding site. lin-Benzo-ATP is a substrate for the phosphotransferase activities of protein kinase with peptides, water, or type II regulatory subunit as phosphoryl acceptors. With Leu-Arg-Arg-Ala-Ser-Leu-Gly as phosphoryl acceptor, the Km for lin-benzo-ATP is 11.3 microM, and that for ATP is 11.9 microM. The Vmax with lin-benzo-ATP is 20% of the Vmax with ATP as the substrate [24.9 +/- 1.8 mumol/(min . mg) vs. 5.0 +/- 1.2 mumol/(min . mg)]. Thus lin-benzo-ATP is the best nucleotide substrate (besides ATP) for the catalytic subunit reported. 1,N6-Etheno-ATP (epsilon ATP), on the other hand, is a poor substrate for the catalytic subunit with a Km of 1.8 mM and a Vmax that is 4% of the Vmax for ATP, making it unsuitable as a fluorescence probe for cAMP-dependent protein kinase.

Cyclic adenosine 3':5'-monophosphate-dependent protein kinase. Comparison of type II enzymes from bovine brain, skeletal muscle, and cardiac muscle.

The physical and chemical properties of purified catalytic and regulatory subunits of type II cAMP-dependent protein kinase from bovine brain, skeletal muscle, and cardiac muscle were compared. The catalytic subunits from all three sources were identical with respect to molecular weight (Mr = 40,000), amino acid composition, and isoelectric points. Furthermore, two-dimensional maps of their tryptic peptides were identical. The type II regulatory subunits from brain and skeletal muscle exhibited identical molecular weights by sodium dodecyl sulfate-gel electrophoresis and both undergo autophosphorylation; however, they differ somewhat in amino acid composition. Furthermore, two-dimensional tryptic peptide maps showed that 40% of the peptides differ and 60% co-migrate. Autoradiography of the peptide maps showed that the main phosphorylated peptide from these two sources also differ. The bovine brain type II regulatory subunit also differed from that of bovine cardiac muscle in the same manner. The molecular weights, amino acid composition, and tryptic peptide maps of the bovine skeletal and cardiac muscle regulatory subunits, however, were experimentally identical. These results suggest that type II protein kinases from bovine brain and muscle (skeletal or cardiac) represent distinct species which differ in their regulatory subunits but share a common catalytic subunit. The tryptic peptide map of the type I regulatory subunit from bovine skeletal muscle was very different from that of the two classes of type II regulatory subunit. There were, however, four polar peptides from neural and nonneural type II subunits as well as the type I regulatory subunit which co-migrated.