Characterization and crystallization of a recombinant IgE Fab fragment in complex with the bovine β-lactoglobulin allergen

A D1 Fab fragment containing the allergen‐binding variable domains of the IgE antibody was characterized by ESI FT–ICR mass spectrometry and crystallized with bovine β‐lactoglobulin (BLG) using the hanging‐drop vapour‐diffusion method at 293 K. X‐ray data suitable for structure determination were collected to 2.8 Å resolution using synchrotron radiation. The crystal belonged to the orthorhombic space group P212121, with unit‐cell parameters a = 67.0, b = 100.6, c = 168.1 Å. The three‐dimensional structure of the D1 Fab fragment–BLG complex will provide the first insight into IgE antibody–allergen interactions at the molecular level.