Amino acid sequence of equine platelet tropomyosin. Correlation with interaction properties.

Equine platelet beta tropomyosin (247 residues), like rabbit skeletal muscle alpha tropomyosin (284 residues) has a repeating pattern of amino acid residues characteristic of a coiled-coil structure. When compared with the muscle protein, it is extended by 5 residues at the NH2-terminus and possesses two 21 residue deletions (positions 23-43 and 60-80 of the muscle sequence). The two proteins are highly conserved from residues 81-260, but are significantly different at their COOH-termini (residues 261-284). These differences in platelet tropomyosin can be correlated with its diminished head-to-tail polymerization, a weaker interaction with F-actin and a reduced affinity for muscle troponin and the T1 fragment of troponin-T.