Identification of membrane-bound calcium, calmodulin-dependent protein kinase II in canine heart.
Phospholamban, the putative regulatory proteolipid of the Ca2+/Mg2+ ATPase in cardiac sarcoplasmic reticulum, was selectively phosphorylated by a Ca2+/calmodulin (CaM)-dependent protein kinase associated with a cardiac membrane preparation. This kinase also catalyzed the phosphorylation of two exogenous proteins known to be phosphorylated by the multifunctional Ca2+/CaM-dependent protein kinase II (Ca2+/CaM-kinase II), i.e., smooth muscle myosin light chains and glycogen synthase a. The latter protein was phosphorylated at sites previously shown to be phosphorylated by the purified multifunctional Ca2+/CaM-kinase II from liver and brain. The membrane-bound kinase did not phosphorylate phosphorylase b or cardiac myosin light chains, although these proteins were phosphorylated by appropriate, specific calmodulin-dependent protein kinases added exogenously. In addition to phospholamban, several other membrane-associated proteins were phosphorylated in a calmodulin-dependent manner. The principal one exhibited a Mr of approximately 56,000, a value similar to that of the major protein (57,000) in a partially purified preparation of Ca2+/CaM-kinase II from the soluble fraction of canine heart that was autophosphorylated in a calmodulin-dependent manner. These data indicate that the membrane-bound, calmodulin-dependent protein kinase that phosphorylates phospholamban in cardiac membranes is not a specific calmodulin-dependent kinase, but resembles the multifunctional Ca2+/CaM-kinase II. Our data indicate that this kinase may be present in both the particulate and soluble fractions of canine heart.
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004285:Dogs; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D000099211:Phospholamban
D017301:Ca(2+) Mg(2+)-ATPase; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D008565:Membrane Proteins; D011494:Protein Kinases; D000099211:Phospholamban