MOLECULAR-IDENTIFICATION OF THE LOBSTER MUSCLE PROTEIN TROPOMYOSIN ASA SEAFOOD ALLERGEN

Crustaceans are a major cause of seafood allergy, Recent studies have identified tropomyosin as the major allergen in shrimp. However, such data are lacking in other crustaceans, In the present study lobster al lergens were identified and characterized by molecular cloning, sequen cing, and expression. An IgE-reactive complementary DNA clone of 2 kil obase pairs (kb) was identified by screening an expression library of the spiny lobster Panulirus stimpsoni using sera from subjects with cr ustacean allergy. Expression and sequencing of this clone showed that it has an opening reading frame of 274 amino acids, coding far a 34-kD a protein designated as Pan s I. In addition, we expressed the fast mu scle tropomyosin from the American lobster Homarus americanus and foun d that this protein, coined Horn a I, was also recognized by IgE from patients with crustacean allergies. The deduced amino acid sequences o f Pan s I and Hom a I, which are the first identified lobster allergen s, show significant homology to shrimp tropomyosin. Sera from subjects with crustacean allergies, when pre-absorbed with recombinant protein s Pan s I or Hom a I, lost their IgE reactivity to muscle extract of P . stimpsoni and H. americanus. Preincubation of crustacean allergy ser a with the recombinant shrimp tropomyosin Met e I also removed their I gE reactivity to lobster muscle extracts. The results suggest that pat ients with allergic reactions to crustaceans have common and possibly cross-reactive IgE-reactive epitopes in lobster and shrimp.