Classification of tropomyosin components into an alpha-like or a beta-like family by partial peptide mapping

Tropomyosins can be classified as belonging to an alpha-like or a beta-like family depending on the absence or presence, respectively in their protease-V8 digestion pattern of two peptides with an apparent molecular mass of 21 kDa. Chicken cardiac tropomyosin and the 43 kDa component from gizzard tropomyosin are accordingly classified as alpha-like tropomyosins, while the 33 kDa gizzard tropomyosin component is a beta-like tropomyosin. The 21 kDa peptides have an overall charge which is more positive than that of the intact tropomyosin or any other tropomyosin peptide and probably contain the -NH2 half of the molecule.