Phosphorylation of chicken cardiac C-protein by calcium/calmodulin-dependent protein kinase II.
Chicken cardiac C-protein was readily phosphorylated by purified calcium/calmodulin-dependent protein kinase II (CaM-kinase II). Maximum incorporation was about 4 mol of 32P/mol of C-protein subunit. Peptide mapping indicated that some of the sites phosphorylated by CaM-kinase II were located on the same phosphopeptides obtained when C-protein was phosphorylated by the cAMP-dependent protein kinase (peptides T1, T2, and T3). There was a fourth peptide (T3a) which was unique to CaM-kinase II phosphorylation. 32P-Amino acid analysis showed that essentially all of the 32P of peptides T1, T2, and T3a was in phosphoserine. cAMP-dependent protein kinase incorporated 32P only into threonine of peptide T3. Threonine was the preferred site of phosphorylation by CaM-kinase II, but there was significant phosphorylation of a serine in peptide T3. Partially purified C-protein preparations contained an associated calcium/calmodulin-dependent protein kinase. Peptide maps obtained from C-protein phosphorylated by the endogenous kinase were similar to those obtained from C-protein phosphorylated by CaM-kinase II. However, the ratio of phosphothreonine to phosphoserine in peptide T3 was lower. This was due to a contaminating phosphatase in the partially purified C-protein which preferentially dephosphorylated the phosphothreonine of peptide T3. It is suggested that the calcium/calmodulin-dependent protein kinase associated with C-protein is similar or identical to CaM-kinase II and that CaM-kinase II may play a role in the phosphorylation of C-protein in the heart.
Schlender
K K
KK
Department of Pharmacology, Medical College of Ohio, Toledo 43699-0008.
Bean
L J
LJ
D000818:Animals; D001345:Autoradiography; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002352:Carrier Proteins / Q000378:metabolism*; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D014357:Trypsin
D002352:Carrier Proteins; C020723:citrate-binding transport protein; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D014357:Trypsin