Purification, crystallization and preliminary X-ray diffraction analysis of 3-ketoacyl-CoA thiolase A1887 from Ralstonia eutropha H16

The gene product of A1887 from Ralstonia eutropha (ReH16_A1887) has been annotated as a 3-ketoacyl-CoA thiolase, an enzyme that catalyzes the fourth step of β-oxidation degradative pathways by converting 3-ketoacyl-CoA to acyl-CoA. ReH16_A1887 was overexpressed and purified to homogeneity by affinity and size-exclusion chromatography. The degradative thiolase activity of the purified ReH16_A1887 was measured and enzyme-kinetic parameters for the protein were obtained, with K_m, V_max and k_cat values of 158 µM, 32 mM min⁻¹ and 5 × 10⁶ s⁻¹, respectively. The ReH16_A1887 protein was crystallized in 17% PEG 8K, 0.1 M HEPES pH 7.0 at 293 K and a complete data set was collected to 1.4 Å resolution. The crystal belonged to space group P4₃2₁2, with unit-cell parameters a = b = 129.52, c = 114.13 Å, α = β = γ = 90°. The asymmetric unit contained two molecules, with a solvent content of 58.9%.