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Barley gamma 3-hordein: Glycosylation at an atypical site, disulfide bridge analysis, and reactivity with IgE from patients allergic to wheat

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Snegaroff, Jacques, J. | Bouchez-Mahiout, Isabelle, I. | Smaali, Mohamed, M. | Pecquet, Catherine, C. | Raison-Peyron, Nadia, N. | Jolivet, Pascale, P. | Laurière, Michel, M.

Edité par CCSD ; Elsevier -

Post translational modifications of a seed storage protein, barley gamma 3-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 gamma 3-hordein molecules trafficked through the Golgi apparatus. Disulfide bridges in native gamma 3-hordein were almost the same as those found in wheat gamma 46-gliadin, except the bridge involving the cysteine included in the glycosylation site. IgE reacted more strongly towards the recombinant than the natural gamma 3-hordein protein. IgE binding to gamma 3-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 gamma 3-hordein due to sequence homology with wheat allergens rather than through shared carbohydrate determinants. (C) 2012 Elsevier B.V. All rights reserved.

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