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

Author: Koppelman, S.J. · Bruijnzeel-Koomen, C.A.F.M. · Hessing, M. · Jongh, H.H.J. de
Type:article
Date:1999
Source:Journal of Biological Chemistry, 8, 274, 4770-4777
Identifier: 234950
doi: doi:10.1074/jbc.274.8.4770
Keywords: Allergen · Allergenicity · Animal cell · Conformational transition · Heat tolerance · Isoelectric point · Nonhuman · Peanut · Priority journal · Protein denaturation · Protein family · Protein folding · Protein secondary structure · Solubility · Thermostability · Adult · Allergens · Arachis hypogaea · Calorimetry, Differential Scanning · Chromatography, Gel · Circular Dichroism · Glycoproteins · Heat · Humans · Immunoglobulin E · Plant Proteins · Protein Conformation · Spectrophotometry, Ultraviolet · Animalia · Ara · Arachis hypogaea

Abstract

Ara h 1, a major peanut allergen was isolated, and its structure on secondary, tertiary, and quaternary level at ambient temperature was investigated using spectroscopic and biochemical techniques. Ara h 1 appeared to be a highly structured protein on a secondary level, possesses a clear tertiary fold, and is present as a trimeric complex. Heat treatment of purified Ara h I results in an endothermic, irreversible transition between 80 and 90 °C, leading to an increase in β-structures and a concomitant aggregation of the protein. Ara h 1 from peanuts that were heat-treated prior to the purification procedure exhibited a similar denatured state with an increased secondary folding and a decreased solubility. The effect of heat treatment on the in vitro allergenic properties of Ara h 1 was investigated by means of a fluid-phase IgE binding assay using serum from patients with a clinically proven peanut allergy. Ara h 1 purified from peanuts heated at different temperatures exhibited IgE binding properties similar to those found for native Ara h 1, indicating that the allergenicity of Ara h 1 is heat-stable. We conclude that the allergenicity of Ara h 1 is unaffected by heating, although native Ara h 1 undergoes a significant heat-induced denaturation on a molecular level, indicating that the recognition of conformational epitopes of Ara h 1 by IgE either is not a dominant mechanism or is restricted to parts of the protein that are not sensitive to heat denaturation.