Mechanism of autophosphorylation of the multifunctional Ca2+/calmodulin-dependent protein kinase.
The multifunctional Ca2+/calmodulin-dependent protein kinase purified from rat brain cytosol undergoes a self-phosphorylation or autophosphorylation reaction. Our conclusion that this reaction is autocatalytic is based on the following lines of evidence: The autophosphorylation reaction and the protein kinase activity toward other substrates are absolutely dependent on the presence of both Ca2+ and calmodulin; autophosphorylation and phosvitin kinase activity show a similar time course and indistinguishable heat lability; the reaction is a consistent property of every preparation of rat brain kinase; the reaction is present in both crude and highly purified preparations of similar kinases or isozymes from rat lung, spleen, heart, bovine brain, and a neuronal tissue from Aplysia californica, a marine mollusk; phosphorylation of the kinase subunits is not mimicked by addition of cAMP, cGMP, Ca2+ plus diglyceride, or addition of the cAMP-dependent protein kinase, and is not blocked by the heat-stable inhibitor protein of the cAMP-dependent protein kinase; and the reaction is intramolecular. Autophosphorylation results in the stoichiometric incorporation of phosphate into both the 51,000- and 60,000-dalton subunits.
D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology; D066298:In Vitro Techniques; D007700:Kinetics; D008970:Molecular Weight; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
D002147:Calmodulin; D011494:Protein Kinases; D002118:Calcium