Tropomyosins are present in muscle and non-muscle cells. In striated muscle, they mediate the interactions between the troponin complex and actin so as to regulate muscle contraction . The role of tropomyosin in smooth muscle and non-muscle tissues is not clear . Tropomyosin is an α-helical protein that forms a coiled-coil structure of two parallel helices containing two sets of seven alternating actin binding sites.
Tropomyosins were identified as minor inhalative allergens in arthropods (mites, cockroaches) and as major food allergens in crustaceans, mollusks, and the fish parasite Anisakis simplex . Vertebrate tropomyosins seem to be non-allergenic. Due to their repetitive coiled-coil structures, tropomyosins retain their IgE binding ability even after prolonged heating or partial digestion. Tropomyosin sequences are highly conserved, which explains the frequent cross-sensitization among distantly related allergen sources.
Family-defining Pfam domains (at least one of these domains is present in each family member):
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