Tropomyosin, in association with the troponin complex, plays a central role in the calcium dependent regulation of muscle contraction (PubMed:9113409, PubMed:11901171). Involved in muscle actin filament organization and muscle arm extension and morphology (PubMed:15930100). Protects actin filaments from depolymerization by unc-60 in vitro (PubMed:17684058). Also has a role in male mating behavior by regulating the copulatory spicules (PubMed:16399684). Binds to F-actin (PubMed:11901171). Isoform a and isoform d are expressed in body wall muscles, vulva, anus muscles and male tail muscles (PubMed:7666414). Located to the myofibrils of thin actin filaments (PubMed:11901171, PubMed:17684058). The molecule is in a coiled coil structure that is formed by 2 polypeptide chains. The sequence exhibits a prominent seven-residues periodicity. Worms have 50-75% embryonic lethality (PubMed:15930100). Those that survive body wall interference have abnormal body morphology and uncoordinated movements, and those that survive pharynx interference have deformed pharynges and gut regions (PubMed:15930100). RNAi-mediated knockdown results in a wavy appearance of the actin filaments in adult body wall muscles (PubMed:17684058). Belongs to the tropomyosin family.