Structural Analysis of Human Alpha-Class Glutathione Transferase A1-1 in the Apo-Form and in Complexes With Ethacrynic Acid and Its Glutathione Conjugate

Structure. 1995 Jul 15;3(7):717-27. doi: 10.1016/s0969-2126(01)00206-4.

Abstract

Background: Glutathione transferases (GSTs) constitute a family of isoenzymes that catalyze the conjugation of the tripeptide glutathione with a wide variety of hydrophobic compounds bearing an electrophilic functional group. Recently, a number of X-ray structures have been reported which have defined both the glutathione- and the substrate-binding sites in these enzymes. The structure of the glutathione-free enzyme from a mammalian source has not, however, been reported previously.

Results: We have solved structures of a human alpha-class GST, isoenzyme A1-1, both in the unliganded form and in complexes with the inhibitor ethacrynic acid and its glutathione conjugate. These structures have been refined to resolutions of 2.5 A, 2.7 A and 2.0 A respectively. Both forms of the inhibitor are clearly present in the associated electron density.

Conclusions: The major differences among the three structures reported here involve the C-terminal alpha-helix, which is a characteristic of the alpha-class enzyme. This helix forms a lid over the active site when the hydrophobic substrate binding site (H-site) is occupied but it is otherwise disordered. Ethacrynic acid appears to bind in a non-productive mode in the absence of the coenzyme glutathione.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoenzymes / chemistry*
  • Apoenzymes / metabolism
  • Binding Sites
  • Crystallography, X-Ray / methods
  • Ethacrynic Acid / analogs & derivatives
  • Ethacrynic Acid / metabolism*
  • Glutathione / analogs & derivatives*
  • Glutathione / metabolism*
  • Glutathione Transferase / chemistry*
  • Glutathione Transferase / metabolism*
  • Humans
  • Isoenzymes / chemistry*
  • Isoenzymes / metabolism
  • Macromolecular Substances
  • Models, Molecular
  • Protein Structure, Secondary*

Substances

  • Apoenzymes
  • Isoenzymes
  • Macromolecular Substances
  • Glutathione Transferase
  • Glutathione
  • Ethacrynic Acid