Characterization of a novel allergen, a major IgE-binding protein from Aspergillus flavus, as an alkaline serine protease

Aspergillus species of fungi have been known to be one of the most prevalen t aeroallergens. One important A flavus allergen (Asp fl 1) was identified by means of immunoblotting with a serum pool of allergic patients on a two- dimensional electrophoretic gel. The cDNA coding for Asp fl 1 was cloned an d sequenced. The clone encodes a full-length protein of 403 amino acid prec ursors of 42 kDa. After cleavage of a putative signal peptide of 21 amino a cids and a prepeptide of 100 amino acids, a mature protein of 282 amino aci ds was obtained with a molecular mass of 33 kDa and a pi of 6.3, A degree o f identity was found in a range of 27 to 84% among related allergens derive d from bacteria allergen subtilisin, mold allergen Pen c 1, and virulence f actor of A. fumigatus. Recombinant Asp fl 1 (rAsp fl 1) was cloned into vec tor pQE-30 and expressed in E. coli M15 as a histidine-tag fusion protein a nd purified to homogeneity, The IgE binding capacity of rAsp fi 1 was teste d by immunoblotting using a serum pool of Aspergillus-allergic patients. Re combinant allergen cross-reacted strongly with IgE specific for natural Asp fl 1 and Pen c 1, indicating that common IgE epitopes may exist between al lergens of A. flavus and P. citrinum. (C) 1999 Academic Press.