Identification and analysis of a conserved immunoglobulin E-binding epitope in soybean G1a and G2a and peanut Ara h 3 glycinins.
To identify conserved immunoglobulin E (IgE)-binding epitopes among legume glycinins, we utilized recombinant soybean G2a and G2a-derived polypeptide fragments. All of these fusion polypeptides bound IgE, and the C-terminal 94-residue fragment appeared to bind more IgE. Using synthetic peptides we identified S219-N233 (S(219)GFAPEFLKEAFGVN(233)) as the dominant IgE-binding epitope. Alanine scanning of this epitope indicated that six amino acids (E224, F225, L226, F230, G231, and V232) contributed most to IgE binding. Among these amino acids, only G231 of soybean G2a is not conserved in soybean G1a (S234) and peanut Ara h 3 (Q256). Synthetic peptides corresponding to the equivalent regions in G1a and Ara h 3 bound IgE in the order Ara h 3>/=soybean G2a>soybean G1a. This sequence represents a new IgE-binding epitope that occurs in a highly conserved region present in legume glycinins. Such IgE-binding sites could provide a molecular explanation for the IgE cross-reactivity observed between soybean and peanut proteins.
Xiang
Ping
P
Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE 68588-0664, USA.
Beardslee
Tom A
TA
Zeece
Michael G
MG
Markwell
John
J
Sarath
Gautam
G
D000485:Allergens / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D010367:Arachis; D017124:Conserved Sequence; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D007887:Fabaceae; D005916:Globulins / Q000737:chemistry / Q000378:metabolism*; D007073:Immunoglobulin E / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D055314:Seed Storage Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D030262:Soybean Proteins; D013025:Glycine max
D000485:Allergens; D052179:Antigens, Plant; D000939:Epitopes; D005916:Globulins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C118207:allergen Ara h3; D007073:Immunoglobulin E; C011474:glycinin