Disorder-to-order transition of the active site of human class Pi glutathione transferase, GST P1-1

Biochemistry. 2001 Oct 2;40(39):11660-9. doi: 10.1021/bi010909+.

Abstract

Glutathione transferases comprise a large family of cellular detoxification enzymes that function by catalyzing the conjugation of glutathione (GSH) to electron-deficient centers on carcinogens and other toxins. NMR methods have been used to characterize the structure and dynamics of a human class pi enzyme, GST P1-1, in solution. Resonance assignments have been obtained for the unliganded enzyme and the GSH and S-hexylglutathione (GS-hexyl) complexes. Differences in chemical shifts between the GSH and GS-hexyl complexes suggest more extensive structural differences between these two enzyme-ligand complexes than detected by previous crystallographic methods. The NMR studies reported here clearly show that an alpha-helix (alpha2) within the GSH binding site exists in multiple conformations at physiological temperatures in the absence of ligand. A single conformation of alpha2 is induced by the presence of either GSH or GS-hexyl or a reduction in temperature to below 290 K. The large enthalpy of the transition ( approximately 150 kJ/mol) suggests a considerable structural rearrangement of the protein. The Gibbs free energy for the transition to the unfolded form is on the order of -4 to -6 kJ/mol at physiological temperatures (37 degrees C). This order-to-disorder transition contributes substantially to the overall thermodynamics of ligand binding and should be considered in the design of selective inhibitors of class pi glutathione transferases.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Glutathione Transferase / chemistry
  • Glutathione Transferase / metabolism*
  • Humans
  • Ligands
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Temperature

Substances

  • Ligands
  • Recombinant Proteins
  • Glutathione Transferase