C-terminal cysteine residues determine the IgE binding of Aspergillus fumigatus allergen Asp f 2.
The knowledge of the structure function relationship of the allergen is essential to design allergenic variants with reduced IgE binding capacity but intact T cell reactivity. Asp f 2 is a major allergen from the fungus Aspergillus fumigatus and >90% of A. fumigatus-sensitized individuals displayed IgE binding to Asp f 2. In the present study, we evaluated the involvement of C-terminal cysteine residues in IgE binding conformation of Asp f 2. The deletion mutants were constructed by adding three C-terminal cysteines of the native Asp f 2 one at a time to the non-IgE binding Asp f 2 (68-203). The point mutants of Asp f 2 (68-268) with C204A and C257A substitutions were constructed to study the role of C-terminal cysteines in IgE binding. Immunological evaluation of reduced and alkylated Asp f 2 and its mutants were conducted to determine the contribution of free sulfhydryl groups as well as the disulfide bonds in allergen Ab interaction. Four-fold increase in IgE Ab binding of Asp f 2 (68-267) compared with Asp f 2 (68-266) and complete loss in IgE binding of C204A mutant of Asp f 2 (68-268) indicate the involvement of C(204) and C(267) in IgE binding conformation of Asp f 2. A significant reduction in IgE binding of wild and mutated Asp f 2 after reduction and alkylation emphasizes the importance of cysteine disulfide bonds in epitope Ab interaction. The hypoallergenic variants may be explored further to develop safe immunotherapeutic strategy for allergic disorders.
Banerjee
Banani
B
Allergy Immunology Division, Department of Pediatrics, Medical College of Wisconsin, Milwaukee 53226, USA. banerjee@mcw.edu
Kurup
Viswanath P
VP
Greenberger
Paul A
PA
Kelly
Kevin J
KJ
Fink
Jordan N
JN
D000485:Allergens / Q000097:blood / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D019943:Amino Acid Substitution / Q000235:genetics; D001229:Aspergillosis, Allergic Bronchopulmonary / Q000097:blood / Q000276:immunology; D001232:Aspergillus fumigatus / Q000276:immunology*; D001666:Binding Sites, Antibody / Q000235:genetics; D003545:Cysteine / Q000737:chemistry* / Q000235:genetics; D004220:Disulfides / Q000737:chemistry; D000939:Epitopes / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D005656:Fungal Proteins / Q000097:blood / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D005822:Genetic Vectors / Q000138:chemical synthesis / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017384:Sequence Deletion / Q000276:immunology; D013329:Structure-Activity Relationship
D000485:Allergens; D004220:Disulfides; D000939:Epitopes; D005656:Fungal Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C106810:allergen Asp f 2, Aspergillus fumigatus; D007073:Immunoglobulin E; D003545:Cysteine