Tropomyosin, in association with the troponin complex, plays a central role in the calcium dependent regulation of muscle contraction. Homodimer. Expressed in mantle muscle (at protein level). The molecule is in a coiled coil structure that is formed by 2 polypeptide chains. The sequence exhibits a prominent seven-residues periodicity. The N-terminus is blocked. Causes an allergic reaction in human (PubMed:16904802, PubMed:8939158, PubMed:17147442, PubMed:25530105). Binds to IgE of patients allergic to crustaceans (shrimp and crab) (PubMed:16904802). Binds to IgE of patients residing in Japan and China allergic to squid (PubMed:8939158, PubMed:17147442, PubMed:25530105). Binds to IgE of American patients allergic to shrimp (PubMed:8939158). The allergenicity of this protein is reduced significantly by its reaction of lysines with ribose during the Maillard reaction (glycation), and to a lesser extent by digestion with pepsin. On the other hand, modification of the lysine residues in this protein using 2,4,6-trinitrobenzenesulfonic acid (TNBS) has no effect on allergenicity (PubMed:17147442). Treatment by high hydrostatic pressure (HHP) reduces allergenicity (400 and 600 MPa more effectively than 200 MPa) (PubMed:25530105). The reaction of this protein with ribose in the Maillard reaction may be useful in development of processed seafood with low allergenicity. Belongs to the tropomyosin family.