Crystallization and preliminary crystallographic investigation of glycosomal pyruvate phosphate dikinase from Trypanosoma brucei

The PP_i-dependent glycosomal enzyme pyruvate phosphate dikinase (PPDK) from Trypanosoma brucei is expressed in the insect stage of the parasite. Its precise function there is still unclear, but the enzyme may catalyze the `reverse reaction' of transfer of phosphate from phosphoenolpyruvate (PEP) to generate pyruvate as a means of scavenging large amounts of pyrophosphate. This protein may represent a target for drug design against diseases caused by trypanosomes and related kinetoplastids. The recombinant protein is 918 amino acids long (predicted molecular mass ≃ 100 kDa and pI = 8.9). Crystallization conditions for the recombinant PPDK are reported that result in crystals that diffract X-rays to better than 3.0 Å resolution. Their space group is P2₁2₁2, with unit-cell parameters a = 121.17, b = 153.5, c = 65.46 Å, α = β = γ = 90°. The crystals, like the protein in solution, are sensitive to temperature and fail to diffract or diffract only to low resolution after ageing for two weeks or longer.