Characterization of Pen n 13, a major allergen from the mold Penicillium notatum

Penicillium notatum is a well-known indoor aeroallergen and is frequently i ncluded in skin test panels for allergic diagnosis. On two-dimensional immu noblotting using patients' sera containing IgE and monoclonal antibody D7B8 specific for Pen c 1 of P. citrinum, two allergens with a molecular mass o f 33 kDa but different isoelectric points were identified. A novel cDNA cod ing for Pen n 13 was cloned and sequenced. The nucleotide sequence codes fo r a protein 397 amino acids including a putative signal peptide of 25 amino acids and a propeptide of 90 amino acids. The allergen is an alkaline seri ne protease that shares more than 39% identical residues with other kinds o f mold allergens. The coding cDNA of Pen n 13 was cloned into vector pQE-30 and expressed in E. coli M15 as a His-tag fusion protein and purified to h omogeneity. The fusion protein reacted with monoclonal antibodies of Pen c 1 and with IgE from Penicillium-allergic patients. Furthermore, it also cro ss-reacted strongly with IgE specific for the natural Pen c 1, indicating t hat similar IgE binding epitopes may exist in the allergens of P, notatum a nd P. citrinum, Antigenicity index plots indicated that there are several s imilar epitope regions of high antigenic indices in Pen c 1 and Pen n 13, c orroborating that mold allergens belonging to the alkaline serine protease family possess similar protein structure and strong antigenic cross-reactiv ity. (C) 2000 Academic Press.