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 symptoms in a patient, who develops into allergy to mustard spice.

OBJECTIVE

To determine the presence of allergenic proteins in rapeseed flour, and analyse the structure of the main component and its crossreactivity with the mustard allergen.

METHODS

SDS-PAGE (sodium dodecyl sulfate-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 liquid chromatography were used to obtain the peptides from the allergenic BnIII napin from rapeseed flour. Automatic Edman degradations were carried out to determine their amino acid sequences, which were compared with other sequences in nucleotide and amino acid sequence databases. Crossreactivity assays were carried out by ELISA inhibition using sera from a rapeseed allergic patient and from patients allergic to mustard.

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 analysis. The protein consists of two different chains of 9.5 and 4.5 kDa. Their complete amino acid sequences were determined. The protein exhibited structural relationships with other napin-like storage proteins from seeds. IgE and IgG crossreactivity between rapeseed and mustard allergens was also demonstrated. Considering the structural and immunological data, certain polypeptide regions are suggested to be involved in the allergenicity of these proteins.

CONCLUSIONS

Rapeseed contains 2S storage proteins which may cause allergy in hypersensitive individuals. These proteins exhibit great sequence similarity with 2S albumins from different seeds. Crossreactivity between mustard and rapeseed flours can be explained by sequence homology.