Large Conformational Changes in the Catalytic Cycle of Glutathione Synthase

Abstract

Glutathione synthase catalyzes the final ATP-dependent step in glutathione biosynthesis, the formation of glutathione from γ-glutamylcysteine and glycine. We have determined structures of yeast glutathione synthase in two forms: unbound (2.3 Å resolution) and bound to its substrate γ-glutamylcysteine, the ATP analog AMP-PNP, and two magnesium ions (1.8 Å resolution). These structures reveal that upon substrate binding, large domain motions convert the enzyme from an open unliganded form to a closed conformation in which protein domains completely surround the substrate in the active site.