In Saccharomyces cerevisiae, as in higher eucaryotes, cyclic AMP (cAMP)-dependent protein kinase is a tetramer composed of two catalytic (C) subunits and two regulatory (R) subunits. In the absence of cAMP, the phosphotransferase activity of the C subunit is inhibited by the tight association with R. Mutation of Thr-241 to Ala in the C1 subunit of S. cerevisiae reduces the affinity of this subunit for the R subunit approximately 30-fold and results in a monomeric cAMP-independent C subunit. The analogous residue in the mammalian C subunit is known to be phosphorylated. Peptide maps of in vivo 32P-labeled wild-type C1 and mutant C1(Ala241) suggest that Thr-241 is phosphorylated in yeast cells. Substituting Thr-241 with either aspartate or glutamate partially restored affinity for the R subunit. Uncharged and positively charged residues substituted at this site resulted in C subunits that failed to associate with the R subunit. Replacement with the phosphorylatable residue serine resulted in a C subunit with wild-type affinity for the R subunit. Analysis of this protein revealed that it appears to be phosphorylated on Ser-241 in vivo. These data suggest that the interaction between R and C involves a negatively charged phosphothreonine at position 241 of yeast C1, which can be mimicked by either aspartate, glutamate, or phosphoserine.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|