Tropomyosin, in association with the troponin complex, plays a central role in the calcium dependent regulation of muscle contraction. Homodimer. Expressed in muscle (at protein level) (PubMed:23393908). Expressed in claw muscles (PubMed:9819304). 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. Natural and recombinant protein binds to IgE of patients allergic to crabs (PubMed:9819304, PubMed:23393908). Recombinant protein binds to IgE in all 10 patients tested allergic to crustaceans. Cross-reacts with greasyback shrimp topomyosin allergen Met e 1.0101 and Chinese spiny lobster tropomyosin allergen Pan s 1 (PubMed:9819304). Cross-reacts with blue swimmer crab tropomyosin allergen Por p 1 (PubMed:23393908). Belongs to the tropomyosin family.