The amino acid sequence of rabbit cardiac tropomyosin.

The amino acid sequence of rabbit cardiac tropomyosin has been investigated by the isolation of peptides derives from cyanogen bromide and proteolytic degradations. Based on identical amino acid compositions, electrophoretic mobilities, and in some cases, NH2-terminal analyses, all peptides were shown to be the same as peptides in the amino acid sequence of rabbit skeletal alpha-tropomyosin. The apparent heterogeneity of the cardiac protein previously observed on alkaline-urea polyacrylamide electrophoresis gels is attributable to a phosphorylated species. We conclude that the primary structures of the cardiac and skeletal alpha component are identical. Differences in actin-linked calcium regulation in skeletal and cardiac muscle must reside largely in the troponin components.