Biological activities of bovine cardiac-muscle troponin C C-terminal peptide (residues 84-161).
1. Bovine cardiac-muscle troponin C was digested at cysteine residues 35 and 84, and the C-terminal peptide (residues 84-161) was isolated. 2. The C-terminal peptide contains two Ca2+-binding sites. These sites bind Ca2+ with a binding constant of 2.0 X 10(8) M-1. In the presence of 2 mM-Mg2+ the binding constant for Ca2+ is decreased to 3.7 X 10(7) M-1. The corresponding constants for native troponin C are 5.9 X 10(7) M-1. and 2.9 X 10(7) M-1 respectively. 3. Electrophoretic mobility of the C-terminal peptide is increased in the presence of 0.1 mM-CaCl2 as compared with the mobility in the presence of 2mM-EDTA. The same phenomenon was observed when electrophoresis was performed in the presence of 6 M-urea or 0.1% sodium dodecyl sulphate. 4. When saturated with Ca2+, the C-terminal peptide forms complexes with bovine cardiac-muscle troponin I both in the absence and in the presence of 6 M-urea. This complex is dissociated on removal of Ca2+. 5. The data suggest that the C-terminal peptide of troponin C contains two Ca2+/Mg2+-binding sites and interacts with troponin I. Thus, despite the 30% difference in amino acid composition, the properties of bovine cardiac-muscle troponin C C-terminal peptide are similar to those of rabbit skeletal-muscle troponin C C-terminal peptide.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*; D019209:Troponin C
D000596:Amino Acids; D009124:Muscle Proteins; D010446:Peptide Fragments; D014336:Troponin; D019209:Troponin C; D002118:Calcium