ISOLATION AND CHARACTERIZATION OF A MAJOR ALLERGEN FROM ORIENTAL MUSTARD SEEDS, BRAJ-I

A 2 S albumin from oriental mustard (Brassica juncea) seeds has been isolated and characterized as an allergen. This protein, Bra j I, was recognized by human IgE from mustard-sensitive individuals, as proved by using two different enzyme immunoassays. Bra j I was found to be closely related to Sin a I, the major allergen from yellow mustard seeds. Many fractions with molecular weights ranging from 16,000 to 16,400 and with differences in charge were separated by ion-exchange chromatography. They exhibited small but significant amino acid composition differences for Glx, Val, Ile, Lys, and Arg contents. The heterogeneity of Bra j I can be explained by size and charge differences of its heavy and light chains. All of the isoallergenic forms of Bra j I gave a single precipitation band in double diffusion immunoassays when using a Sin a-I-specific rabbit polyclonal serum.