A NOVEL CA2+ CALMODULIN-DEPENDENT PROTEIN-KINASE LACKING AUTOPHOSPHORYLATION ACTIVITY IN THE RABBIT HEART/

We report the discovery, semi-purification and characterization of a n ovel Ca2+/calmodulin-dependent protein kinase (peak I kinase) using sy ntide 2 as a substrate from the rabbit heart. In the study of dependen ce of peak I kinase on the concentration of calmodulin, half-maximal a ctivation was obtained at approx. 2.0 x 10(-7) M calmodulin. Peak I ki nase did not undergo autophosphorylation. This kinase phosphorylates t he synthetic peptides such as syntide 2, autocamtide-2, site 3 in a Ca 2+/CaM-dependent manner, but not myosin light chain-peptide, gamma-pep tide, and cAMP Response Element Binding Protein (CREB) peptide. Elonga tion Factor-2, alpha-casein and histone-IIIs were not phosphorylated. These data indicate that this CaM kinase is different from other ident ified Ca2+/calmodulin-dependent protein kinases and therefore constitu tes a novel protein kinase. (C) 1995 Academic Press, Inc.