THE ISOLATION, PURIFICATION, AND PRELIMINARY CRYSTALLOGRAPHIC CHARACTERIZATION OF UDP-GALACTOSE-4-EPIMERASE FROM ESCHERICHIA-COLI

Uridine diphosphogalactose-4-epimerase from E. coli has been crystallized in a form suitable for a high-resolution X-ray crystallographic structural analysis. The enzyme complexed with a substrate analogue, uridine diphosphobenzene (UDP-benzene), crystallizes readily using polyethylene glycol 8000 as the precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)21(1) with unit cell dimensions, a = 76.3 angstrom, b = 83.1 angstrom, and c = 132.1 angstrom. Based on still setting photographs, the crystals diffract to a nominal resolution of 2.3 angstrom and are stable in the X-ray beam. The enzyme used in these experiments was produced by a new expression system and a modified purification scheme.