DETECTION, ISOLATION AND COMPLETE AMINO-ACID-SEQUENCE OF AN AEROALLERGENIC PROTEIN FROM RAPESEED FLOUR

Background Seed proteins have been found to cause hypersensitivity by ingestion or inhalation. Rapeseed flour was responsible for allergic s ymptoms in a patient, who develops into allergy to mustard spice. Obje ctive To determine the presence of allergenic proteins in rapeseed flo ur, and analyse the structure of the main component and its crossreact ivity with the mustard allergen. Methods SDS-PAGE (sodium dodecyl sulf ate-polyacrylamide gel electrophoresis) and subsequent immunoblotting with a serum from a rapeseed allergic patient were performed to detect IgE-binding proteins. Proteolytic digestions and high performance liq uid chromatography were used to obtain the peptides from the allergeni c BnIII napin from rapeseed flour. Automatic Edman degradations were c arried out to determine their amino acid sequences, which were compare d with other sequences in nucleotide and amino acid sequence databases . Crossreactivity assays were carried out by ELISA inhibition using se ra from a rapeseed allergic patient and from patients allergic to must ard. Results The 2S albumins of rapeseed were recognized by the serum from a patient allergic to this seed. The most abundant isoform of the allergenic napins, BnIII, was used for structural and immunological a nalysis. The protein consists of two different chains of 9.5 and 4.5 k Da. Their complete amino acid sequences were determined. The protein e xhibited structural relationships with other napin-like storage protei ns from seeds. IgE and IgG crossreactivity between rapeseed and mustar d allergens was also demonstrated. Considering the structural and immu nological data, certain polypeptide regions are suggested to be involv ed in the allergenicity of these proteins. Conclusions Rapeseed contai ns 2S storage proteins which may cause allergy in hypersensitive indiv iduals. These proteins exhibit great sequence similarity with 2S album ins from different seeds. Crossreactivity between mustard and rapeseed flours can be explained by sequence homology.