EXPRESSION, CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF LIGAND-FREE HUMAN GLUTATHIONE-S-TRANSFERASE M2-2

Human glutathione-S-transferase M2-2 (hGSTM2-2) was expressed in Esche richia coli and purified by GSH-affinity chromatography. The recombina nt enzyme and the protein isolated from human tissue were indistinguis hable based on physicochemical, enzymatic and immunological criteria. The catalytically active dimeric hGSTM2-2 was crystallized without GSH or other active-site ligands in two crystal forms. Diffraction from f orm A crystals extends to 2.5 Angstrom and is consistent with the spac e group P2(1) (a = 53.9, b = 81.5, c = 55.6 Angstrom, beta = 109.26 An gstrom) with two monomers in the asymmetric unit. Diffraction from for m B crystals extends to 3 Angstrom and is consistent with a space grou p P2(1)2(1)2(1) (a = 57.2, b = 80.7, c = 225.9 Angstrom) with two dime rs in the asymmetric unit. This is the first report of ligand-free mu- class GST crystals, and a comparison with liganded complexes will prov ide insight into the structural consequences of substrate binding whic h are thought to be important for catalysis.