C-Terminal 23�kDa polypeptide of soybean Gly�m�Bd 28�K is a potential allergen

Abstract

Gly m Bd 28 K is a major soybean (Glycine max Merr.) glycoprotein allergen. It was originally identified as a 28 kDa polypeptide in soybean seed flour. However, the full-length protein is encoded by an open reading frame (ORF) of 473 amino acids, and contains a 23 kDa C-terminal polypeptide of as yet unknown allergenic and structural characteristics. IgE-binding (allergenic potential) of the Gly m Bd 28 K protein including the 23 kDa C-terminal portion as well as shorter fragments derived from the full-length ORF were evaluated using sera from soy-sensitive adults. All of these sera contained IgE that efficiently recognized the C-terminal region. Epitope mapping demonstrated that a dominant linear C-terminal IgE binding epitope resides between residues S256 and A270. Alanine scanning of this dominant epitope indicated that five amino acids, Y260, D261, D262, K264 and D266, contribute most towards IgE-binding. A model based on the structure of the b subunit of soybean b-conglycinin revealed that Gly m Bd 28 K contains two cupin domains. The dominant epitope is on the edge of the first b-sheet of the C-terminal cupin domain and is present on a potentially solvent-accessible loop connecting the two cupin domains. Thus, the C-terminal 23 kDa polypeptide of Gly m Bd 28 K present in soy products is allergenic and apparently contains at least one immunodominant epitope near the edge of a cupin domain. This knowledge could be helpful in the future breeding of hypoallergenic soybeans.

Proteomic analysis of the distribution of the major seed allergens in wild, landrace, ancestral, and modern soybean genotypes

“…There is very little additional information about variation in this allergen among different soybean genotypes. A mutant line of soybean G. max, cv Tohoku 124, with the absence of β-conglycinin also lacks Gly m Bd 28 K. 30 Xiang et al 39 demonstrated that both the Nand C-terminal fragments of Gly m Bd 28 K can bind IgE, and have characterized a novel dominant sequential epitope on the C-terminal fragment of the protein. Tsuji et al 40 reported that Gly m Bd 28 K was about twice as large as anticipated from its initial discovery as a 28 kDa polypeptide by onedimensional SDS-PAGE.…”

Genetic background impacts soluble and cell wall-bound aromatics in brown midrib mutants of sorghum

“…Approximately 30 g of total protein were loaded from each sample and separated on 12% acrylamide gels in the presence of SDS (Laemmli 1970). Separated proteins were electroblotted to nitrocellulose membranes and probed with antibodies (Xiang et al 2004). Antibodies were generated to soybean root nodule ascorbate peroxidase (Dalton et al 1993) and to recombinant proteins produced in E. coli to the following ESTs: DN143131 = switchgrass CAD; DN143927 = switchgrass CCOMT; CX607415 = sorghum COMT.…”

Soybean Allergens: Presence, Detection and Methods for Mitigation

“…Moreover, Gly m Bd 28 K protein shares sequence homology with proteins in pumpkins and carrots (Rihs et al, 1999). Studies revealed a slightly stronger IgE-binding region present in the C-terminal domain of Bd 28K (Xiang et al, 2004) than the N-terminal half of this protein . An important IgE binding region was found in the C-terminal 23 kDa polypeptide, which contains an Asn-N linked moiety with the same sugar composition as that of P34 (Hiemori et al, 2000).…”

“…Gly m. Bd 28K is a vicillin-like glycoprotein of 473 amino acids (Xiang et al, 2004), initially isolated from soybean meal as a 28 kDa glycosylated protein. Gly m Bd 28K (Hiemori et al, 2000) constitutes a minor component fractionated into 11S glycinin globulin fraction in soybean seed flour that has been recognized by soybean sensitive patients with about 25% of incidence .…”