Sequential phosphorylation of skeletal muscle troponin.
Phosphorylation of the isolated rabbit skeletal muscle holotroponin complex at troponin-T by phosphorylase kinase is unusual in that it shows maxima and minima. These oscillations are due to protein phosphatase activity present in the preparations. Following tryptic digestion two phosphorylated peptides, I and II, can be isolated. Their amino-acid compositions are identical and correspond to that of the tryptic peptide which contains the two known phosphorylatable sites 149/150 and 156/7 of troponin-T. Peptide I is phosphorylated on both sites and peptide II only on one site. During phosphorylation the doubly phosphorylated peptide I appears first; after a short lag phase peptide II is formed containing only one phosphate. These phenomena probably cause the observed oscillations in the degree of the holotroponin phosphorylation.
D000818:Animals; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D009132:Muscles / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010764:Phosphorylase Kinase / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D013997:Time Factors; D014336:Troponin / Q000378:metabolism*
D010710:Phosphates; D014336:Troponin; D010764:Phosphorylase Kinase