Barley γ3-hordein: Glycosylation at an atypical site,disulfide bridge analysis,and reactivity with IgE from patients allergic to wheat |
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Authors: | Jacques Snégaroff Isabelle Bouchez Mohamed El Amine Smaali Catherine Pecquet Nadia Raison-Peyron Pascale Jolivet Michel Laurière |
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Institution: | 1. INRA, UMR1318, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France;2. Dermatologie Allergologie, Hôpital Tenon, AP-HP, F-75970 Paris Cedex 20, France;3. Hôpital Saint-Eloi, Service de dermatologie, F-34295 Montpellier Cedex 05, France;4. INRA, UMR 206, Chimie Biologique, AgroParisTech, F-78850 Thiverval-Grignon, France |
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Abstract: | Post translational modifications of a seed storage protein, barley γ3-hordein, were determined using immunochemical and mass spectrometry methods. IgE reactivity towards this protein was measured using sera from patients diagnosed with allergies to wheat. N-glycosylation was found at an atypical Asn-Leu-Cys site. The observed glycan contains xylose. This indicates that at least some γ3-hordein molecules trafficked through the Golgi apparatus. Disulfide bridges in native γ3-hordein were almost the same as those found in wheat γ46-gliadin, except the bridge involving the cysteine included in the glycosylation site. IgE reacted more strongly towards the recombinant than the natural γ3-hordein protein. IgE binding to γ3-hordein increased when the protein sample was reduced. Glycosylation and disulfide bridges therefore decrease epitope accessibility. Thus the IgE from patients sensitized to wheat cross-react with γ3-hordein due to sequence homology with wheat allergens rather than through shared carbohydrate determinants. |
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Keywords: | CAM carbamidomethylated DIG digoxigenin IHHWP immediate hypersensitivity to hydrolyzed wheat protein LMW-GS low molecular weight glutenin subunit TFMS trifluoromethanesulfonic acid WDEIA wheat-dependent exercise-induced anaphylaxis |
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