Purification and characterization of a novel protein activator of Ca2+/calmodulin-dependent protein kinase I.
A protein activator of Ca2+/calmodulin (CaM)-dependent protein kinase I was purified from rat brain. The activator was retained on a CaM-Sepharose column in the presence of Ca2+ and kinase assay of renatured gel revealed the 64 kDa molecule in the purified activator fraction to be autophosphorylated and to phosphorylate recombinant CaM kinase I in the presence of Ca2+/calmodulin. These results suggest that this activator of CaM kinase I is also a CaM-dependent protein kinase. Phosphorylation of CaM kinase I by the activator resulted in drastic potentiation of its CaM-dependent activity. Furthermore, kinetic analyses demonstrated that the activation decreases the Km values of CaM kinase I for both ATP and syntide-2 without a change in Vmax values. Considering the quite low enzymatic activity of recombinant CaM kinase I without activation, the 64 kDa species might be essential for CaM kinase I function in vivo.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000302:isolation & purification* / Q000378:metabolism*; D002846:Chromatography, Affinity; D004789:Enzyme Activation; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D051381:Rats; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011994:Recombinant Proteins; C063391:syntide-2; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517599:Camk1 protein, rat; C517682:Pnck protein, rat