Calcium-binding allergens: From plants to man

Calcium-binding proteins contain a variable number of motifs, termed EF-hands, which consist of two perpendicularly placed α-helices and an inter-helical loop forming a single calcium-binding site. Due to their ability to bind and transport calcium as well as to interact with a variety of ligands in a calcium-dependent manner, they fulfill important biological functions in eukaryotic cells. After parvalbumin, a three EF-hand fish allergen, calcium-binding allergens were discovered in pollens of trees, grasses and weeds and, recently, as autoallergens in man. Although only a small percentage of atopic individuals displays IgE reactivity to calcium-binding allergens, these allergens may be important because of their ability to cross-sensitize allergic individuals. Conformation and stability as well as IgE recognition of calcium-binding allergens greatly depend on the presence of protein-bound calcium ions. It is thus likely that hypoallergenic derivatives of calcium-binding allergens can be engineered by recombinant DNA technology for immunotherapy of sensitized patients.