THE STRUCTURES OF HUMAN GLUTATHIONE TRANSFERASE P1-1 IN COMPLEX WITH GLUTATHIONE AND VARIOUS INHIBITORS AT HIGH-RESOLUTION

The human pi-class glutathione S-transferase (hGST P1-1) is a target f or structure-based inhibitor design with the aim of developing drugs t hat could be used as adjuvants in chemotherapeutic treatment. Here we present seven crystal structures of the enzyme in complex with substra te (glutathione) and two inhibitors (S-hexyl glutathione and mma-gluta myl-(S-benzyl)cysteinyl-D-phenylglycine). The binding of the modified glutathione inhibitor, amma-glutamyl-(S-benzyl)cysteinyl-D-phenylglyci ne, has been characterized with the phenyl group stacking against the benzyl moiety of the inhibitor and making interactions with the active -site residues Phe8 and Trp38. The structure provides an explanation a s to why this compound inhibits the pi-class GST much better than the other GST classes. The structure of the enzyme in complex with glutath ione has been determined to high resolution (1.9 to 2.2 Angstrom) in t hree different crystal forms and at two different temperatures (100 an d 288 K). In one crystal form, the direct hydrogen-bonding interaction between the hydroxyl group of Tyr7, a residue involved in catalysis, and the thiol group of the substrate, glutathione, is broken and repla ced by a water molecule that mediates the interaction. The hydrogen-bo nding partner of the hydroxyl group of Tyr108, another residue implica ted in the catalysis, is space-group dependent. A high-resolution (2.0 Angstrom) structure of the enzyme in complex with S-hexyl glutathione in a new crystal form is presented. The enzyme-inhibitor complexes sh ow that the binding of ligand into the electrophilic binding site does not lead to any conformational changes of the protein. (C) 1997 Acade mic Press Limited.