Phosphorylation of a bovine cardiac actin complex.
A bovine cardiac actin-tropomyosin-troponin complex was phosphorylated in the presence of [gamma-32P]ATP, Mg2+, adenosine 3',5'-monophosphate (cyclic AMP), and bovine cardiac cyclic-AMP-dependent protein kinase. Approximately 81% of the [32P]phosphate incorporated was identified as phosphoserine and phosphothreonine. Gel electrophoresis studies showed that 55% of the [32P]phosphate was associated with the inhibitory component of troponin (Tn-I) and 24% with a protein resembling the tropomyosin-binding component of troponin in the actin complex, respectively. The phosphorylation of Tn-I in the actin complex was inhibited 30% when Ca2+ was increased from 0.1 to 50 muM, but phosphorylation of other components was not affected by increasing Ca2+ concentration. Half-maximal calcium activation of the ATPase activity of reconstituted actomyosins made with the [32P]phosphorylated cardiac actin complex and cardiac myosin was shifted to Ca2+ values higher than those of actomyosins made with the nonphosphorylated actin complex.
D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002417:Cattle; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*
D000199:Actins; D009124:Muscle Proteins; D014335:Tropomyosin; D014336:Troponin; D000205:Actomyosin; D011494:Protein Kinases; D000252:Calcium-Transporting ATPases; D002118:Calcium