Direct identification of the high and low affinity calcium binding sites of troponin-C

Covalent labelling of the calcium ligands of intact troponin-C (0.1 M KCl, pH 6.0) with [³H] -ethanolamine, at various ratios of calcium to troponin-C followed by analysis of the two separated cleavage products, shows that the first and second calcium binding sites of the sequence are the low affinity sites and that the third and fourth sites are the high affinity or structure defining sites of troponin-C.