Ca2+/calmodulin-dependent protein kinase II is phosphorylated by protein kinase C in vitro.
Protein kinase C (PKC) phosphorylated a synthetic peptide (CBP) that included the Thr-286 phosphorylation sequence and calmodulin binding domain of Ca2+/calmodulin-dependent protein kinase type II (CaM-kinase). Studies with a variety of truncated peptides suggested that the amino acid phosphorylated by PKC was Thr-286, the same amino acid that when autophosphorylated by Ca2+/calmodulin activation of CaM-kinase results in Ca2+/calmodulin-independent activity. These peptide studies also suggested that the C-terminal region of CBP is required to obtain maximal phosphorylation of Thr-286 by PKC. PKC also phosphorylated purified CaM-kinase from rat forebrain. Phosphopeptide analysis by one- and two-dimensional proteolytic maps of autophosphorylated CaM-kinase and CaM-kinase phosphorylated with PKC identified that there are both similar and unique sites phosphorylated. Phosphoamino acid analysis of CaM-kinase phosphorylated by PKC indicated that both Ser and Thr residues were phosphorylated. Even though Thr-286 of CaM-kinase appeared to be phosphorylated by PKC, no Ca2+/calmodulin-independent activity was detected, and, additionally, no significant change in Ca2+/CaM-dependent activation was detected. These results provide the first indication that these two important protein kinases may communicate directly through interenzyme phosphorylation.
Waxham
M N
MN
Department of Neurobiology and Anatomy, University of Texas Health Science Center, Houston 77225.
Aronowski
J
J
D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D016548:Prosencephalon / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D013379:Substrate Specificity
D010446:Peptide Fragments; D010455:Peptides; D010748:Phosphopeptides; D011494:Protein Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases