The site of phosphorylation of troponin I in the perfused rabbit heart. The effect of adrenaline.
1. On treatment of the perfused rabbit heart with adrenaline, the total covalently bound phosphate of troponin I increased from 1.14 mol of phosphate/mol to 1.86 mol of phosphate/mol. 2. Covalently bound phosphate could be identified only in the region of the molecule of cardiac troponin I consisting of residues 1--48. 3. When 32P-labelled orthophosphate was present in the perfusion medium the phosphate at serine-20 became radioactively labelled. This residue was the only significant site of phosphorylation that could be identified. 4. The addition of adrenaline caused a 4--5-fold increase in covalently bound [32P]phosphate. Virtually all of the 32P was located at serine-20. 5. It was concluded from these studies that the extent of phosphorylation of serine-20 of cardiac troponin I increased from 30--40% in the control perfused heart to about 100% in the presence of adrenaline.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001345:Autoradiography; D002850:Chromatography, Gel; D004837:Epinephrine / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010477:Perfusion; D010710:Phosphates / Q000032:analysis; D010766:Phosphorylation; D011817:Rabbits; D014336:Troponin / Q000378:metabolism*
D000596:Amino Acids; D009124:Muscle Proteins; D010446:Peptide Fragments; D010710:Phosphates; D014336:Troponin; D004837:Epinephrine