Characteristic amino acid distribution around segments unique to allergens

Abstract

Epitopes are located at the surface of allergens with which antibodies specifically bind. On the assumption that fragments unique to allergens have common, characteristic amino acid sequences, we compared the amino acid sequences of allergens with those of non-allergens. Segments around fragments unique to allergens showed wavelet-like distributions for several amino acids. Charged residues, alanine and glycine had positive peaks at the centre of the unique segments with small valleys on both sides, while aromatic residues, proline and cysteine showed the inverse distribution. Furthermore, the wavelet-like distribution of amino acids could be represented by a universal distribution function together with an index characterizing the intensity of the wavelet. Using the universal distribution function and the novel index of amino acids, we developed a simple method for extracting segments and fragments that are unique to allergens. The significance of the universal distribution function and the novel index is also discussed, by comparing the plot of the allergen-unique fragments index and dynamic fluctuation in the three dimensional structure of birch pollen allergen as both a single molecule and a complex with the corresponding antibody.