Biological activities of the peptides obtained by digestion of troponin C and calmodulin with thrombin.
1. Troponin C and calmodulin were not digested by thrombin at a significant rate in the presence of Ca2+. 2. In the presence of EGTA, troponin C was digested by thrombin to yield three peptides, TH1 (residues 1--120), TH3 (residues 1--100) and TH2 (residues 121--159). 3. In the presence of EGTA calmodulin was digested by thrombin giving two peptides, TM1 (residues 1--106) and TM2 (residues 107--148). 4. The electrophoretic mobilities of peptides TH1 and TM1 were increased at pH 8.6 by Ca2+ both in the presence and absence of urea. The mobilities of peptides TH2 and TM2 were unaltered under these conditions. 5. Peptides TH1, TH2 and tM1 formed complexes with troponin I on polyacrylamide gels at pH 8.6 in the presence of Ca2+. 6. The phosphorylation of troponin I by cyclic AMP-dependent protein kinase was significantly inhibited by peptides TH1 and TH3 and to a lesser extent by peptide TM1. 7. The calmodulin peptide TM1 activated myosin light-chain kinase when present in large molar excess. Peptide TM2 did not activate the enzyme.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001923:Brain Chemistry; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D008274:Magnesium; D009124:Muscle Proteins; D009219:Myosin-Light-Chain Kinase; D010446:Peptide Fragments / Q000302:isolation & purification* / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D011817:Rabbits; D013917:Thrombin; D014336:Troponin; D019209:Troponin C
D000596:Amino Acids; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D009124:Muscle Proteins; D010446:Peptide Fragments; D014336:Troponin; D019209:Troponin C; D011494:Protein Kinases; D009219:Myosin-Light-Chain Kinase; D013917:Thrombin; D008274:Magnesium; D002118:Calcium