The amino-acid sequence of chicken fast-skeletal-muscle troponin I

The amino acid sequence of troponin I from chicken breast and leg muscle has been determined using tryptic and CNBr peptides. The protein contains 182 residues and has a molecular weight of 21136. The N-terminus is blocked and is probably acetylated. 35 of the residues have acidic and 45 have basic side chains giving an overall net positive charge of 9. The CNBr peptides from both breast and leg troponin I have been shown to be identical and no heterogeneity has been found in the tryptic peptides isolated from a mixture of the two proteins. It may thus be taken that the two proteins are identical. Comparison with the sequence of troponin I from rabbit fast skeletal muscle shows strong homology with 34 differences out of 182 residues. The major difference is in a deletion of three residues, from 152 to 154, in the rabbit protein.