Determination of the complete amino acid sequence of bovine cardiac troponin C.

The amino acid sequence of bovine cardiac troponin C has been completely determined. The protein was cleaved by cyanogen bromide and the resulting peptides were isolated. All of the 161 residues of the protein could be accounted for in 12 cyanogen bromide peptides. Overlapping peptides were generated by tryptic digestion of citraconylated troponin C and isolation of the resulting five peptides. The primary structure of cardiac troponin C was elucidated by sequential manual Edman degradation of these peptides. It consists of four homologous regions, one of which probably has lost the ability to bind calcium ions. By comparing the amino acid sequence of cardiac troponin C with the sequence of skeletal troponin C, it was found that the mutation rate of the region that does not bind calcium is almost twice as high as the mutation rate of the three homologous regions that do bind calcium.