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

Equine platelet β tropomyosin (247 residues), like rabbit skeletal muscle α tropomyosin (284 residues) has a repeating pattern of amino acid residues characterisitic of a coiled-coil structure. When compared with the muscle protein, it is extended by 5 residues at the NH 2-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 diminshed head-to-tail polymerization, a weaker interaction with F-actin and a reduced affinity for muscle troponin and the T1 fragment of troponin-T.