Dataset Information

Co-induction of a glutathione-S-transferase, a glutathione transporter and an ABC transporter in maize by xenobiotics.

ABSTRACT: Glutathione conjugation reactions are one of the principal mechanisms that plants utilize to detoxify xenobiotics. The induction by four herbicides (2,4-D, atrazine, metolachlor and primisulfuron) and a herbicide safener (dichlormid) on the expression of three genes, ZmGST27, ZmGT1 and ZmMRP1, encoding respectively a glutathione-S-transferase, a glutathione transporter and an ATP-binding cassette (ABC) transporter was studied in maize. The results demonstrate that the inducing effect on gene expression varies with both chemicals and genes. The expression of ZmGST27 and ZmMRP1 was up-regulated by all five compounds, whereas that of ZmGT1 was increased by atrazine, metolachlor, primisulfuron and dichlormid, but not by 2,4-D. For all chemicals, the inducing effect was first detected on ZmGST27. The finding that ZmGT1 is activated alongside ZmGST27 and ZmMRP1 suggests that glutathione transporters are an important component in the xenobiotic detoxification system of plants.

SUBMITTER: Pang S

PROVIDER: S-EPMC3394700 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Co-induction of a glutathione-S-transferase, a glutathione transporter and an ABC transporter in maize by xenobiotics.

Pang Sen S Duan Liusheng L Liu Zhiqian Z Song Xiaoyu X Li Xuefeng X Wang Chengju C

PloS one 20120711 7

Glutathione conjugation reactions are one of the principal mechanisms that plants utilize to detoxify xenobiotics. The induction by four herbicides (2,4-D, atrazine, metolachlor and primisulfuron) and a herbicide safener (dichlormid) on the expression of three genes, ZmGST27, ZmGT1 and ZmMRP1, encoding respectively a glutathione-S-transferase, a glutathione transporter and an ATP-binding cassette (ABC) transporter was studied in maize. The results demonstrate that the inducing effect on gene exp ...[more]

PMID: 22792398

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Project description:The isoenzyme glutathione S-transferase (GST) I from maize (Zea mays) was cloned and expressed in Escherichia coli, and its catalytic mechanism was investigated by site-directed mutagenesis and dynamic studies. The results showed that the enzyme promotes proton dissociation from the GSH thiol and creates a thiolate anion with high nucleophilic reactivity by lowering the pK(a) of the thiol from 8.7 to 6.2. Steady-state kinetics fit well to a rapid equilibrium, random sequential Bi Bi mechanism, with intrasubunit modulation between the GSH binding site (G-site) and the electrophile binding site (H-site). The rate-limiting step of the reaction is viscosity-dependent, and thermodynamic data suggest that product release is rate-limiting. Five residues of GST I (Ser(11), His(40), Lys(41), Gln(53) and Ser(67)), which are located in the G-site, were individually replaced with alanine and their structural and functional roles in the 1-chloro-2,4-dinitrobenzene (CDNB) conjugation reaction were investigated. On the basis of steady-state kinetics, difference spectroscopy and limited proteolysis studies it is concluded that these residues: (1) contribute to the affinity of the G-site for GSH, as they are involved in side-chain interaction with GSH; (2) influence GSH thiol ionization, and thus its reactivity; (3) participate in k(cat) regulation by affecting the rate-limiting step of the reaction; and (4) in the cases of His(40), Lys(41) and Gln(53) play an important role in the structural integrity of, and probably in the flexibility of, the highly mobile short 3(10)-helical segment of alpha-helix 2 (residues 35-46), as shown by limited proteolysis experiments. These structural perturbations are probably transmitted to the H-site through changes in Phe(35) conformation. This accounts for the modulation of K(CDNB)(m) by His(40), Lys(41) and Gln(53), and also for the intrasubunit communication between the G- and H-sites. Computer simulations using CONCOORD were applied to maize GST I monomer and dimer structures, each with bound lactoylglutathione, and the results were analysed by the essential dynamics technique. Differences in dynamics were found between the monomer and the dimer simulations showing the importance of using the whole structure in dynamic analysis. The results obtained confirm that the short 3(10)-helical segment of alpha-helix 2 (residues 35-46) undergoes the most significant structural rearrangements. These rearrangements are discussed in terms of enzyme catalytic mechanism.

Dataset Information

Co-induction of a glutathione-S-transferase, a glutathione transporter and an ABC transporter in maize by xenobiotics.

Publications

Co-induction of a glutathione-S-transferase, a glutathione transporter and an ABC transporter in maize by xenobiotics.

Similar Datasets

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