Crystallization and Preliminary X-ray Diffraction Studies of Recombinant Human Ornithine Aminotransferase

Abstract

Human liver ornithine aminotransferase was expressed in Escherichia coli and purified by ammonium sulfate fractionation and anion exchange column chromatography. The purified recombinant enzyme is fully active and crystallized readily over a wide range of polyethylene glycol concentrations. The crystals belong to the trigonal space group P3 121 (or its enantiomorph P3 221) with unit cell parameters a = b = 116.3 Å, and c = 190.0 Å, α = β = 90°, γ = 120°. There are three monomers per asymmetric unit. Self-rotation function studies revealed both 2-fold and 3-fold non-crystallographic symmetry with the local 3-fold axis being tilted 15° from the c axis and perpendicular to a crystallographic dyad. A complete native data set to 2.3 Å resolution was collected using synchrotron radiation.