Tropomyosin, in association with the troponin complex, plays a central role in the calcium dependent regulation of muscle contraction. May also regulate motor systems required to maintain nuclear integrity and apico-basal polarity during embryogenesis. Homodimer. The molecule is in a coiled coil structure that is formed by 2 polypeptide chains. The sequence exhibits a prominent seven-residues periodicity. Pre-cellular embryos exhibit abnormal nuclear divisions with frequent loss of chromosome fragments. During cellularization, apico-basal polarity is also disrupted. Belongs to the tropomyosin family.