Tropomyosin: An invertebrate pan-allergen

Among food allergens, crustaceans, such as shrimp, crab, crawfish and lobst er, are a frequent cause of adverse food reactions in allergic individuals. The major allergen has been identified as the muscle protein tropomyosin. This molecule belongs to a family of highly conserved proteins with multipl e isoforms found in both muscle and nonmuscle cells of all species of verte brates and invertebrates. Its native structure consists of two parallel alp ha-helical tropomyosin molecules that are wound around each other forming a coiled-coil dimer. Allergenic tropomyosins are found in invertebrates such as crustaceans (shrimp, lobster, crab, crawfish), arachnids (house dust mi tes), insects (cockroaches), and mollusks (e.g. squid), whereas vertebrate tropomyosins are nonallergenic. Studies of cross-reactivities among crustac eans and the high degree of sequence identity among them suggest that tropo myosin is probably the common major allergen in crustaceans. Furthermore, i mmunological relationships between crustaceans, cockroaches and housedust m ites have been established and may suggest tropomyosin as an important cros s-sensitizing pan allergen.