Homology of Two cDNAs Coding for Birch Pollen Allergens with Calmodulin: Protein-Bound Ca2+ Affects the IgE-Binding...

Birch pollen is known to contain two well-defined allergens, Bet v I, a protein, which is a major allergen for 95% of the birch-pollen-allergic individuals, and birch profilin, which we could identify as a novel type of plant pan allergen. Here, we report the identification of two novel birch pollen allergens with significant sequence homology to calmodulin. Although both allergens are rear targets for patients' IgE (5-10%), we consider them of particular interest because both proteins require the native protein conformation and protein-bound Ca2+ for IgE binding. Thus we describe for the first time an IgE epitope which is assembled by a polypeptide and a divalent cation, Ca2+.