Heat-induced conformational changes of Ara h 1, a major peanut allergen, do not affect its allergenic properties

Ara h 1, a major peanut allergen was isolated, and its structure on seconda ry, tertiary, and quaternary level at ambient temperature was investigated using spectroscopic and biochemical techniques. Ara h 1 appeared to be a hi ghly structured protein on a secondary level, possesses a clear tertiary fo ld, and is present as a trimeric complex. Heat treatment of purified Ara h 1 results in an endothermic, irreversible transition between 80 and 90 degr ees C, leading to an increase in beta-structures and a concomitant aggregat ion of the protein. Ara h 1 from peanuts that were heat-treated prior to th e purification procedure exhibited a similar denatured state with an increa sed secondary folding and a decreased solubility, The effect of heat treatm ent on the in vitro allergenic properties of Ara h 1 was investigated by me ans of a fluid-phase IgE binding assay using serum from patients with a cli nically proven peanut allergy. Ara h 1 purified from peanuts heated at diff erent temperatures exhibited IgE binding properties similar to those found for native Ara h 1, indicating that the allergenicity of Ara h 1 is heat-st able. We conclude that the allergenicity of Ara h 1 is unaffected by heatin g, although native Ara h 1 undergoes a significant heat-induced denaturatio n on a molecular level, indicating that the recognition of conformational e pitopes of Ara h 1 by IgE either is not a dominant mechanism or is restrict ed to parts of the protein that are not sensitive to heat denaturation.