Calmodulin-dependent protein kinases purified from rat brain and rabbit liver.
A calmodulin-dependent protein kinase was purified from rat brain by the same protocol used previously for a rabbit liver calmodulin-dependent glycogen synthase kinase. The rat brain kinase readily phosphorylated rabbit skeletal muscle glycogen synthase at sites 1b and 2, the same sites phosphorylated by rabbit liver calmodulin-dependent kinase. The two kinases have other similarities: substrate specificity, potent inhibition by sodium fluoride, and nearly equal Ka's (10-20 nM) for calmodulin. Also, both enzymes have similar Stokes radii, 70 A (rabbit liver) and 75 A (rat brain), but quite different sedimentation coefficients, 10.6 S and 17.4 S, respectively. Consequently, the calculated molecular weights are also different: 560,000 for the brain enzyme and 300,000 for the liver enzyme. The major subunit of the rat brain kinase appears to be a single 51-kDa peptide, not a doublet pattern of 51- and 53-kDa subunits that is characteristic of the rabbit liver enzyme. Our findings are consistent with the hypothesis that the rat brain and rabbit liver enzymes belong to a class of closely related calmodulin-dependent protein kinases, possibly isozymes. This class of enzymes may be responsible for regulating several of the known calcium-dependent physiological functions.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002147:Calmodulin / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification*; D011817:Rabbits; D051381:Rats; D012969:Sodium Fluoride / Q000494:pharmacology; D013379:Substrate Specificity
D002147:Calmodulin; D046911:Macromolecular Substances; D012969:Sodium Fluoride; D006006:Glycogen Synthase; D011494:Protein Kinases