title: Mutations that prevent cyclic nucleotide binding to binding sites A or B of type I cyclic AMP-dependent protein kinase.
abstract: Cyclic nucleotide binding and activation properties of cAMP-dependent protein kinases from five independent mutants of S49 mouse lymphoma cells were studied. These mutants were all hemizygous for expression of mutant regulatory (R) subunits of the type I kinase with lesions that altered the electrostatic charge of R subunit: lesions in three of the mutants mapped to cAMP-binding site A, and those in two of the mutants mapped to cAMP-binding site B. A nucleotide mismatch assay using 32P-labeled cRNA and ribonuclease A confirmed and refined localization of the mutations to single amino acid residues implicated in cAMP binding. R subunits from all mutants retained the ability to bind cAMP, but binding behaved as if it were entirely to nonmutated sites: 1) relative affinities of 11 adenine-modified derivatives of cAMP for mutant enzymes were identical to their relative affinities for the site of wild-type kinase that corresponded to the nonmutated site of the mutant; 2) the potencies of these analogs as activators of mutant kinases were strictly correlated with their binding affinities (for wild-type enzyme activation potencies were correlated with mean affinities of the analogs for cAMP-binding sites A and B); 3) combinations of analogs with strong preferences for opposite cAMP-binding sites in wild-type kinase showed no synergism in activating mutant kinases; 4) dissociation of cAMP from mutant kinases was monophasic; and 5) high salt accelerated dissociation of cAMP from kinases with site B lesions but retarded dissociation from those with site A lesions.
authors.affiliation: Cell Biology Research Group, University of Bergen, Norway.
authors.forename: D
authors.initials: D
authors.lastname: Ogreid
authors.forename: S O
authors.initials: SO
authors.lastname: Døskeland
authors.forename: K B
authors.initials: KB
authors.lastname: Gorman
authors.forename: R A
authors.initials: RA
authors.lastname: Steinberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000235:genetics; D004789:Enzyme Activation; D008223:Lymphoma; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D004273:DNA, Neoplasm; D046911:Macromolecular Substances; D000242:Cyclic AMP; D011494:Protein Kinases