CHARACTERIZATION OF FERN SPORE ALLERGENS OF SINGAPORE -- WITH SPECIAL REFERENCE TO DICRANOPTERIS SPP

Abstract

Spores from some local ferns were found to contain allergens. Among these, spores from the Dicranopteris linearis and Dicranopteris curranii ferns were significantly more reactive. A 6.5 kDa major allergen from these two fern spores was isolated and identified. Its protein sequence show homology to the 2S seed storage protein. Carbohydrate moiety played an important role in the constitution or its lgE epitopes. Genes encoding this 6.5 kDa allergen from Dicranopteris curranii and Dicranopteris linearis were isolated which contain an open reading frame that defined a 125-residue protein of molecular weight 14611 daltons. The precursor contained a conspicuous signal peptide and sequences of a large and a small subunit. Signal peptide cleavage site and post-translational processing site were confirmed by both nucleic acid and protein sequence analysis as well as enzymatic digestion. The expressed protein could not be recognized by positive sera indicating that the carbohydrate components affected the specific lgE binding to the protein.