[Phosphorylation of troponin in the heart and skeletal muscle by Ca2+-phospholipid-dependent protein kinase].
The phosphorylation of the whole troponin complex and of the cardiac and skeletal troponin components by Ca2+-phospholipid-dependent protein kinase was studied. The activity of enzyme isolated from rat brain by ion-exchange chromatography on DEAE-Sephadex and by affinity chromatography on phosphatidylserine immobilized on polyacrylamide gel was shown to be completely dependent on Ca2+ and phospholipids and was equal to 0.4-0.6 mumol of phosphate/min.mg protein with histone H1 as substrate. The resulting preparation of Ca2+-phospholipid-dependent protein kinase was able to phosphorylate the isolated troponin I; the amount of phosphate transferred per mol of cardiac and skeletal troponin I was equal to 1.1 and 0.4, respectively. The maximal degree of phosphorylation of isolated troponin T by Ca2+-phospholipid-dependent protein kinase was 0.6 mol of phosphate per mol of troponin T both for skeletal and cardiac proteins. The rate and degree of phosphorylation were independent of the initial level of troponin T phosphorylation. Ca2+-phospholipid-dependent protein kinase did not phosphorylate the first serine residue of troponin T, i.e., the site which was phosphorylated in the highest degree after isolation of troponin T from skeletal muscles. The data obtained and the fact that the rate and degree of phosphorylation of troponins I and T within the whole troponin complex are 10-20 times less than those for isolated components provide little evidence for the participation of protein kinase C in troponin phosphorylation in vivo.
Vorotnikov
A V
AV
Risnik
V V
VV
Gusev
N B
NB
D000818:Animals; D001921:Brain / Q000201:enzymology; D002417:Cattle; D009132:Muscles / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D013379:Substrate Specificity; D014336:Troponin / Q000378:metabolism*; D019210:Troponin I; D020107:Troponin T
D014336:Troponin; D019210:Troponin I; D020107:Troponin T; D011493:Protein Kinase C
Fosforilirovanie troponina serdtsa i skeletnykh myshts Ca2+-fosfolipidzavisimoĭ proteinkinazoĭ.