Download MendeleyCrystal structure of a dimerized cockroach allergen Bla g 2 complexed with a monoclonal antibody.
Li, M., Gustchina, A., Alexandratos, J., Wlodawer, A., Wunschmann, S., Kepley, C.L., Chapman, M.D., Pomes, A.(2008) J Biol Chem 283: 22806-22814
- PubMed: 18519566
- DOI: https://doi.org/10.1074/jbc.M800937200
- Primary Citation of Related Structures:
2NR6 - PubMed Abstract:
The crystal structure of a 1:1 complex between the German cockroach allergen Bla g 2 and the Fab' fragment of a monoclonal antibody 7C11 was solved at 2.8-angstroms resolution. Bla g 2 binds to the antibody through four loops that include residues 60-70, 83-86, 98-100, and 129-132. Cation-pi interactions exist between Lys-65, Arg-83, and Lys-132 in Bla g 2 and several tyrosines in 7C11. In the complex with Fab', Bla g 2 forms a dimer, which is stabilized by a quasi-four-helix bundle comprised of an alpha-helix and a helical turn from each allergen monomer, exhibiting a novel dimerization mode for an aspartic protease. A disulfide bridge between C51a and C113, unique to the aspartic protease family, connects the two helical elements within each Bla g 2 monomer, thus facilitating formation of the bundle. Mutation of these cysteines, as well as the residues Asn-52, Gln-110, and Ile-114, involved in hydrophobic interactions within the bundle, resulted in a protein that did not dimerize. The mutant proteins induced less beta-hexosaminidase release from mast cells than the wild-type Bla g 2, suggesting a functional role of dimerization in allergenicity. Because 7C11 shares a binding epitope with IgE, the information gained by analysis of the crystal structure of its complex provided guidance for site-directed mutagenesis of the allergen epitope. We have now identified key residues involved in IgE antibody binding; this information will be useful for the design of vaccines for immunotherapy.
Organizational Affiliation:
Macromolecular Crystallography Laboratory, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.
