Novel bovine heart calmodulin-dependent protein kinase which phosphorylates a high molecular weight calmodulin-binding protein.

A novel calmodulin-dependent protein kinase has been isolated from bovine cardiac muscle by successive chromatography on DEAE-Sepharose 6B, Calmodulin-Sepharose 4B affinity and Sepharose 6B chromatography columns. The protein kinase was shown by gel filtration chromatography to have a molecular mass of 36,000 daltons. The highly purified protein kinase stoichiometrically phosphorylated the high molecular weight calmodulin-binding protein from cardiac muscle [Sharma RK (1990) J Biol Chem 265, 1152-1157] in a Ca2+/calmodulin-dependent manner. The phosphorylation resulted in the maximal incorporation of 1 mol of phosphate/mol of the high molecular weight calmodulin-binding protein. Other Ca2+/calmodulin-dependent protein kinases failed to phosphorylate the high molecular weight calmodulin-binding protein. The distinct substrate specificity of this protein kinase indicates that it is not related to the known calmodulin-dependent protein kinases and therefore constitutes a novel protein kinase.