Tropomyosins in gastropods and bivalves: Identification as major allergens and amino acid sequence features

Tropomyosin appears to be a major cross-reactive allergen of crustaceans and molluscs. In this study, four species of gastropods (disc abalone, turban shell, whelk and Middendorf’s buccinum) and seven species of bivalves (bloody cockle, Japanese oyster, Japanese cockle, surf clam, horse clam, razor clam and short-neck clam) were confirmed to be allergenic by ELISA and their major allergen identified as tropomyosin by immunoblotting. Inhibition immunoblotting data showed the cross-reactivity of gastropod and bivalve tropomyosins with one another and also with cephalopod and crustacean tropomyosins. Then, amino acid sequences of tropomyosins from 10 species except for Middendorf’s buccinum were elucidated by cDNA cloning. The known amino acid sequence data including our results reveal that molluscan tropomyosins share low sequence identities (about 60%) with crustacean tropomyosins and that they are highly homologous with one another within the same group (same family or same order) but not among the groups.