Crystallization and preliminary crystallographic data of a Fel d 1 (1+2) construct corresponding to the major allergen from cat

The domestic cat (Felis domesticus) is one of the most important causes of allergic disease worldwide. A homologue of the major allergen Fel d 1 was created by linking the two chains that compose the protein. Fel d 1 (1+2) was expressed in Escherichia coli and subsequently purified using three chromatographic steps. Crystals of Fel d 1 (1+2) were obtained using the hanging-drop vapour-diffusion method in 22.5% PEG 3350, 0.5 M CaCl₂. The crystals belong to space group P1, with unit-cell parameters a = 38.5, b = 42.9, c = 49.0 Å, α = 70.7, β = 80.5, γ = 81.5°, and diffract to 1.6 Å resolution.