Proteolytic processing of the peanut allergen Ara h 3

Publisher Website
Google Scholar
Abstract
The allergen Ara h 3 has been purified recently from peanuts. In contrast to recombinant Ara h 3, a 60 kDa single‐chain polypeptide, the allergen isolated from its native source is extensively proteolytically processed. The characteristic proteolytic processing for 11S plant storage proteins of the glycinin family is observed for Ara h 3 yielding an acidic and a basic subunit, bound by a disulfide bridge. In addition to this, proteolytic truncation is observed for the acidic subunit but not for the basic subunit of Ara h 3. A series of Ara h 3 polypeptides ranging from 13–45 kDa was separated by sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and each band was digested by trypsin. Peptides related to the bands were identified and a scheme positioning the different polypeptides in the Ara h 3 sequence has been constructed. Peptide analysis showed sequence heterogeneity at two positions indicating the presence of multiple genes encoding variant, but highly homologous Ara h 3 proteins. The pool of Ara h 3 polypeptides from its native source illustrated that allergen from the peanut is much more complex than the recombinant protein used for epitope mapping experiments. From several Ara h 3 truncation products one or more immunoglobulin E (IgE) binding sites had been removed. Characterization of the allergenicity of Ara h 3 should therefore also include IgE‐binding studies with peanut‐derived Ara h 3, providing the high degree of variation in the Ara h 3 protein structure, as this is what peanut‐allergic individuals are confronted with.