Complete Amino Acid Sequence of the Catalytic Subunit of Bovine Cardiac Muscle Cyclic AMP-Dependent Protein Kinase

The complete amino acid sequence of the 349-residue catalytic subunit of cyclic AMP-dependent protein kinase from bovine cardiac muscle is presented. The sequence of the subunit (Mr40,580 including phosphate groups at threonine-196 and serine-337) was derived largely by automated Edman degradation of nine fragments generated from the carboxymethylated protein by cleavage of methionyl bonds with cyanogen bromide. These fragments were aligned along the polypeptide chain by analysis of methionine-containing tryptic peptides isolated from protein radiolabeled in vitro by [14C]methyl exchange at methionyl residues. The molecule contains only two cysteinyl residues, at positions 198 and 342. It is relatively polar, containing clusters of cationic residues toward the amino terminus and anionic residues towards the carboxyl terminus. Predictions of secondary structure suggest the presence of three major domains with approximately half of the residues occurring in α -helices and 12% in β -strands.