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United States Department of Agriculture

Agricultural Research Service

Title: Identification and Epitope Analysis of a Soybean Glycinin

Authors
item Helm, Ricki - UAMS, LITTLE ROCK, AR
item Cockrell, Gael - UAMS, LITTLE ROCK, AR
item Connaughton, Cathie - UAMS, LITTLE ROCK, AR
item Sampson, Hugh - MT SINAI MED SCH NEW YORK
item Bannon, Gary - UAMS, LITTLE ROCK, AR
item Beilinson, Vadim - PURDUE UNIVERSITY BIOCHEM
item Nielsen, Niels
item Burks, A - UAMS, LITTLE ROCK, AR

Submitted to: International Archives of Allergy and Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2000
Publication Date: N/A

Interpretive Summary: Food allergies are becoming increasingly important as new foods enter the human food chain. Soy products have a history of eliciting allergic responses in a small but expanding proportion of the population. Sensitivity to soybean products generally involves gastrointestinal disturbances, but they generally becomes less severe as individuals mature. The research described in this communication is focused on the identification of regions on the surface of one of the major soybean allergens to which individuals sensitive to soy products react. The allergen described in the communication is called glycinin. Because it is a seed storage protein, it is one of the most prevalent proteins in the seed. The information will aid scientists who are interested in either developing seeds that lack the allergen, or whose goal is to develop a means to desensitize individuals to soy products.

Technical Abstract: Individuals develop allergic sensitivity to soybean products. The objectives of this study were:1) To identify unique proteins in soybean extracts that bind to specific IgE from soybean-sensitive individuals; 2) Characterize specific B-cell epitopes; 3) Determine if any amino acid were critical to IgE binding; and, 4) Model the allergen to the 3-D phaseolin molecule. Preparative and 2-D SDS-PAGE/IgE immunoblot analysis was used to identify a 21-kD soybean-specific allergen from crude soybean extracts. Amino acid sequence analysis identified the protein as G2 glycinin. B-cell epitopes were identified using SPOTs peptide analysis. Eleven linear epitopes, representing linear 15 amino acid peptide sequences, bound to IgE. One epitope could be rendered non-IgE binding by alanine substitutions in the peptide. Structural orientation of the IgE-binidng regions was mapped to the 3-D phaseolin molecule using molecular modeling of the protein tertiary structure. The epitopes were distributed asymmetrically on the surface of the G2 trimers. The non-random distribution of the IgE binding sites provides new insight about the organization of the trimers in 11S complexes of the G2 glycinin allergen.

Last Modified: 10/25/2014
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