The phosphorylation of troponin I from cardiac muscle.
1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.
D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000032:analysis / Q000378:metabolism; D009206:Myocardium / Q000032:analysis; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010764:Phosphorylase Kinase / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011817:Rabbits; D014336:Troponin / Q000302:isolation & purification / Q000378:metabolism*
D009124:Muscle Proteins; D009943:Organophosphorus Compounds; D014336:Troponin; D000242:Cyclic AMP; D011494:Protein Kinases; D010764:Phosphorylase Kinase