Tropomyosin, in association with the troponin complex, plays a central role in the calcium dependent regulation of muscle contraction. Homodimer. The molecule is in a coiled coil structure that is formed by 2 polypeptide chains. The sequence exhibits a prominent seven-residues periodicity. Causes an allergic reaction in human. Native and recombinant protein binds to IgE in 57% and 43%, respectively, of 14 Thai patients allergic to cockroach P.americana. Belongs to the tropomyosin family.