Isolation and molecular cloning of a major wheat allergen, Tri a Bd 27K

Tri a Bd 27K is the predominant allergen in wheat. In the present study, this allergen was purified to homogeneity from wheat flour. The N-terminal amino acid sequences of the purified allergen and the peptides obtained by its digestion, with trypsin were determined, and the allergen was shown to be a glycoprotein with an Asn-linked sugar moiety containing fucose residues. A cDNA encoding the allergen was obtained by polymerase chain reaction (PCR). The cDNA codes for a protein of 203 amino acid residues, with a molecular mass of 22,803 Da, that has two tentative sites glycosylated at Asn residues. Homology analysis suggested that the allergen might belong to a family of gamma-interferon-inducible thiol reductases. The cDNA was expressed as a fusion protein with glutathione S-transferase in Escherichia coli. However, unlike the allergen purified from wheat, recombinant Tri a Bd 27K was not immunoblotted with IgE antibodies in the serum of a wheat-sensitive patient.