Amino-acid sequence of tropomyosin-binding component of rabbit skeletal muscle troponin.

The complete amino-acid sequence of rabbit skeletal troponin-T is reported. The protein consists of a single polypeptide chain of 259 amino acids; it has an acetylated amino terminus and a molecular weight of 30,503. The sequence was determined by manual and/or automated Edman degradation techniques on the six fragments obtained after cleavage with cyanogen bromide. The larger fragments were further digested with trypsin, chymotrypsin, alpha-lytic protease, thermolysin, or pepsin to obtain smaller fragments suitable for manual sequencing. About 50% of the residues are charged at neutral pH with highly acidic amino-terminal (residues 1-39) and highly basic carboxyl-terminal regions (residues 221-259). Predictions of secondary structure indicate 37% helical content with two long sections (residues 80-102 and 122-146) in that portion of the molecule implicated in binding to tropomyocin. Two of the three phosphorylated sites in the molecule are located at serine-1 and serine-149 or -150. The sequence about the latter site resembles somewhat the phosphorylase kinase phosphorylation sites in phosphorylase alpha and troponin-I.