| Autor: |
Reinemer, Peter, Prade, Lars, Hof, Peter, Neuefeind, Torsten, Huber, Robert, Zettl, Rolf, Palme, Klaus, Schell, Jeff, Koelln, Ingo, Bartunik, Hans D., Bieseler, Barbara |
| Zdroj: |
JMB Online (Journal of Molecular Biology); January 19, 1996, Vol. 255 Issue: 2 p289-309, 21p |
| Abstrakt: |
Glutathione S-transferases (GST) are a family of multifunctional enzymes involved in the metabolization of a broad variety of xenobiotics and reactive endogenous compounds. The interest in plant glutathione S-transferases may be attributed to their agronomic value, since it has been demonstrated that glutathione conjugation for a variety of herbicides is the major resistance and selectivity factor in plants. The three-dimensional structure of glutathione S-transferase from the plantArabidopsis thalianahas been solved by multiple isomorphous replacement and multiwavelength anomalous dispersion techniques at 3 Å resolution and refined to a final crystallographicR-factor of 17.5% using data from 8 to 2.2 Å resolution. The enzyme forms a dimer of two identical subunits each consisting of 211 residues. Each subunit is characterized by the GST-typical modular structure with two spatially distinct domains. Domain I consists of a central four-stranded β-sheet flanked on one side by two α-helices and on the other side by an irregular segment containing three short 310-helices, while domain II is entirely helical. The dimeric molecule is globular with a prominent large cavity formed between the two subunits. The active site is located in a cleft situated between domains I and II and each subunit binds two molecules of a competitive inhibitor S-hexylglutathione. Both hexyl moieties are oriented parallel and fill the H-subsite of the enzyme's active site. The glutathione peptide of one inhibitor, termed productive binding, occupies the G-subsite with multiple interactions similar to those observed for other glutathione S-transferases, while the glutathione backbone of the second inhibitor, termed unproductive binding, exhibits only weak interactions mediated by two polar contacts. A most striking difference from the mammalian glutathione S-transferases, which share a conserved catalytic tyrosine residue, is the lack of this tyrosine in the active site of the plant glutathione S-transferase. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
Full Text from ScienceDirect