CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION STUDIES OF RECOMBINANT HUMAN ORNITHINE AMINOTRANSFERASE

Human liver ornithine aminotransferase was expressed in Escherichia co li and purified by ammonium sulfate fractionation and anion exchange c olumn chromatography. The purified recombinant enzyme is fully active and crystallized readily over a wide range of polyethylene glycol conc entrations. The crystals belong to the trigonal space group P3(1)21 (o r its enantiomorph P3(2)21) with unit cell parameters a = b = 116.3 An gstrom, and c = 190.0 Angstrom, alpha = beta = 90 degrees, gamma = 120 degrees. 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 degrees from the c axis and perpendicular to a crystallographic dyad. A complete native data set to 2.3 Angstrom resolution was collected using synchrotron r adiation.