title: Three-dimensional structure of glutathione S-transferase from Arabidopsis thaliana at 2.2 A resolution: structural characterization of herbicide-conjugating plant glutathione S-transferases and a novel active site architecture.
abstract: 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 plant Arabidopsis thaliana has been solved by multiple isomorphous replacement and multiwavelength anomalous dispersion techniques at 3 A resolution and refined to a final crystallographic R-factor of 17.5% using data from 8 to 2.2 A 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 beta-sheet flanked on one side by two alpha-helices and on the other side by an irregular segment containing three short 3(10)-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.
authors.affiliation: Bayer AG, GB Pflanzenschutz (PF-F Biotechnologie) Pflanzenschutzzentrum Monheim, Leverkusen, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Reinemer
authors.forename: L
authors.initials: L
authors.lastname: Prade
authors.forename: P
authors.initials: P
authors.lastname: Hof
authors.forename: T
authors.initials: T
authors.lastname: Neuefeind
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: R
authors.initials: R
authors.lastname: Zettl
authors.forename: K
authors.initials: K
authors.lastname: Palme
authors.forename: J
authors.initials: J
authors.lastname: Schell
authors.forename: I
authors.initials: I
authors.lastname: Koelln
authors.forename: H D
authors.initials: HD
authors.lastname: Bartunik
authors.forename: B
authors.initials: B
authors.lastname: Bieseler
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D006540:Herbicides / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment
chemical_list: D004791:Enzyme Inhibitors; D006540:Herbicides; D005982:Glutathione Transferase; D005978:Glutathione; C033550:hexylglutathione