Crystallization and preliminary X-ray crystallographic analysis of p24, a component of the potato nuclear factor PBF-2

The Solanum tuberosum (potato) nuclear factor PBF-2 is implicated in pathogen-induced expression of the pathogenesis-related gene PR-­10a. Crystals of the DNA-binding component of PBF-2, p24, have been obtained at 277 K in 20 mM Tris-HCl pH 8.0. Recombinant protein with a His tag at its C-terminus was overexpressed in Escherichia coli in the presence and absence of selenomethionine and was purified using a combination of HiTrap affinity columns and gel-filtration chromatography. Crystals suitable for structural analysis were obtained for both native and selenomethionine-labelled proteins and yielded diffraction data at 100 K that were processed to 2.3 and 2.8 Å resolution, respectively. The p24 protein crystals belong to space group P2₁2₁2₁, with unit-cell parameters a = 69.4 (69.1), b = 89.4 (90.5), c = 144.1 (144.3) Å. The asymmetric unit contains four protomers, giving a crystal volume per protein mass (V_M) of 2.23 Å³ Da^-1 and a solvent content of 45% by volume.