Tropomyosin, the major oyster Crassostrea gigas allergen and its IgE-binding epitopes

The major allergen (Cra g 1) isolated from the oyster Crassostrea gigas was digested with lysylendopeptidase. Twenty-one peptide fragments were isolated from the digest by reverse-phase HPLC and some of them were sequenced. Cra g 1 was identified as tropomyosin. In competitive ELISA inhibition analyses of Iysylendopeptidase fragments, a peptide (K21) showed maximum inhibition of the binding of IgE antibodies in sensitive human serum to Cra g 1. On further tryptic hydrolysis of K21, two peptides exhibited high inhibitory ability equivalent to K21. These results suggested that Cra g 1 had an IgE-binding epitope in the segment 92-105 (IQLLEEDMERSEER) which was dissimilar to those of the major allergen (tropomyosin) from the shrimp Penaeus indicus