[Various properties of cardiac troponin C tryptic peptides]

Using chromatography and preparative polyacrylamide gel electrophoresis, tryptic peptides TP 1 (residues 47-83), TP 2 (residues 84-118) and TP 3 (residues 119-161) were isolated in a highly homogeneous state from cardiac troponin C. Peptides TP 1, TP 2 and TP 3 were found to contain isolated cation-binding sites II, III and IV of cardiac troponin C. The interaction of these peptides with troponins I and T was studied. It was found that only peptide TP 2 could interact with troponin I. Neither of the peptides isolated interacted with troponin T. The cation-binding properties and structural peculiarities of peptide TP 1 were investigated. It was shown that despite its small size (37 amino acid residues), peptide TP 1 retained its ability to bind Ca2+ which caused conformational changes in the peptide structure. This was accompanied by changes in the electrophoretic mobility and absorption of TP 1 on phenyl-Sepharose.