title: Site-specific cyclic nucleotide binding and dissociation of the holoenzyme of cAMP-dependent protein kinase.
abstract: The photoaffinity reagent 8-azidoadenosine 3':5'-monophosphate (8-N3cAMP) was previously shown to modify a single tyrosine residue on the type II regulatory subunit of cAMP-dependent protein kinase (Kerlavage, A.R., and Taylor, S.S. (1980) J. Biol. Chem, 255, 8483-8488). In the present studies, the binding stoichiometries of type II holoenzyme for cAMP and 8-N3cAMP were determined using Millipore filtration assays in the absence (Assay A) and presence (Assay B) of 2 M NaCl and histone. The binding stoichiometry of holoenzyme for cAMP was 2 mol/mol with Assay A, and 4 mol/mol with assay B. The binding stoichiometry for 8-N3cAMP was 2 mol/mol with Assay B or with Assay A following photolysis of the holoenzyme:8-N3cAMP mixture. In the absence of photolysis, the binding stoichiometry for 8-N3cAMP was 0.4 mol/mol with Assay A. Both 8-N3cAMP and cAMP fully dissociated the holoenzyme. Holoenzyme, labeled with 8-N3[3H]cAMP on a preparative scale, incorporated 1 mol of 8-N3[3H]cAMP/mol of regulatory subunit (RII) monomer. The labeled RII was separated from catalytic subunit, cleaved with cyanogen bromide, and the resultant peptides were separated by high performance liquid chromatography. A single radioactive peptide was observed which had the same NH2 terminal residue and amino acid composition as the peptide obtained when dissociated RII was labeled with 8-N3cAMP.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D001386:Azides; D001665:Binding Sites; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D000596:Amino Acids; D001386:Azides; C017042:8-azidoadenosine-3',5'-monophosphate; D000242:Cyclic AMP; D011494:Protein Kinases