N‐terminal sequences of high molecular weight allergens from celery tuber

BACKGROUND: Celery tuber is an important source of food allergens. Low molecular weight celery allergens were identified as homologues of Bet v 1 and profilin. Little is known about the relevant allergens with molecular weights between 45 and 60 kDa, which cross-react with other plant food and pollen allergens. OBJECTIVE: The aim of this study was to isolate cross-reactive, high molecular weight allergens from celery and to characterize them by N-terminal sequencing. METHODS: High molecular weight allergens of celery were identified by immunoglobulin (Ig) E immunoblotting with patients' sera, and the IgE-binding patterns were compared with those of the monoclonal antibirch pollen antibody BIP3, as well as of a polyclonal rabbit anti-Art v 1 antiserum. Two independent methods, elution from preparative SDS-PAGE or anion exchange chromatography, were used to purify the IgE-binding celery proteins of interest. The isolated proteins were examined by N-terminal sequencing and IgE-immunoblots. RESULTS: Celery allergens with molecular masses of 55, 58 and 63 kDa, which were also recognized by the monoclonal BIP3 antibody and a polyclonal anti-Art v 1 antiserum, were isolated. The 63-kDa allergen was N-terminally blocked. The 55- and 58-kDa compounds yielded the same N-terminus, which showed no homology to known proteins in the databases. CONCLUSION: The combination of two independent protein separation techniques, immunoblotting and N-terminal sequencing, identified an N-terminus of two allergens in the 60-kDa molecular weight region. Our data will be helpful for the definite molecular characterization of these important cross-reactive molecules.