Les protéines à motif cupine : allergènes majeurs des graines

Abstract

Major allergens of peanut, tree nuts and other edible seeds, essentially consist of seed storage proteins that are deposited into the protein bodies during the seed ripening process. Globulins with cupin motifs are the most abundant seed storage protein allergens. They are classically subdivided in two groups of 7S and 11S globulins, which correspond to vicilins and legumins, respectively. Vicilins result from the non-covalent association of three single-chain monomers in flattened triangular-shaped homotrimers. Legumins definitely differ from vicilins by homotrimers built up from two-chain monomers, subsequently associated face to face in a homohexameric structure. In addition, vicilins are usually N-glycosylated whereas legumins are essentially non-glycosylated. Both vicilin and legumin proteins are widely distributed as major allergens, e.g. Ara h 1 (vicilin) and Ara h 3 (legumin) of peanut ( Arachis hypogaea), or as putative allergens, e.g. germin (legumin) of chestnut ( Castanea sativa), in edible seeds of different plant families. According to their high degree of both sequential and structural conservation, they often trigger IgE-binding cross-reactions in sensitized individuals. In most cases, however, the clinical significance of these IgE-binding cross-reactivities still remains to be assessed.