C-Terminal 23 kDa polypeptide of soybean Gly m Bd 28 K is a potential allergen.
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 beta subunit of soybean beta-conglycinin revealed that Gly m Bd 28 K contains two cupin domains. The dominant epitope is on the edge of the first beta-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.
Xiang
Ping
P
Department of Biochemistry, University of Nebraska, 332 Keim Hall, East Campus, Lincoln, NE 68583-0939, USA.
Haas
Eric J
EJ
Zeece
Michael G
MG
Markwell
John
J
Sarath
Gautam
G
D000409:Alanine; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D003001:Cloning, Molecular; D004926:Escherichia coli; D006023:Glycoproteins / Q000276:immunology*; D007073:Immunoglobulin E / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology*; D010940:Plant Proteins / Q000276:immunology; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D030262:Soybean Proteins; D013025:Glycine max / Q000737:chemistry* / Q000276:immunology
D000485:Allergens; D052179:Antigens, Plant; C107967:Gly m Bd 28K allergen, Glycine max; D006023:Glycoproteins; D010446:Peptide Fragments; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D030262:Soybean Proteins; D007073:Immunoglobulin E; D000409:Alanine