 The ATP-grasp fold is conserved within the ATP-grasp superfamily and is characterized by two alpha helices and beta sheets that hold onto the ATP molecule between them.The domain containing the active site exhibits interesting properties of specificity.In contrast to γ-glutamylcysteine synthetase, glutathione synthetase accepts a large variety of glutamyl-modified analogs of γ-glutamylcysteine, but is much more specific for cysteine-modified analogs of γ-glutamylcysteine.