Purification and crystallization of the human EF-hand tumour suppressor protein S100A2

Human recombinant tumour suppressor S100A2 and a mutant lacking cysteine residues have been purified and crystallized. Only the crystals of the mutant protein diffracted to appropriate resolution and a complete data set was recorded at 1.7 Å. S100A2 is a Ca²⁺-binding EF-hand protein that is mainly localized in the nucleus. There, it acts as a tumour suppressor by binding and activating p53. Wild-type S100A2 and a S100A2 variant lacking cysteines have been purified. CD spectroscopy showed that there are no changes in secondary-structure composition. The S100A2 mutant was crystallized in a calcium-free form. The crystals, with dimensions 30 × 30 × 70 µm, diffract to 1.7 Å and belong to space group P2₁2₁2₁, with unit-cell parameters a = 43.5, b = 57.8, c = 59.8 Å, α = β = γ = 90°. Preliminary analysis of the X-ray data indicates that there are two subunits per asymmetric unit