1
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Bodourian CS, Poudel N, Papageorgiou AC, Antoniadi M, Georgakis ND, Abe H, Labrou NE. Ligandability Assessment of Human Glutathione Transferase M1-1 Using Pesticides as Chemical Probes. Int J Mol Sci 2022; 23:3606. [PMID: 35408962 PMCID: PMC8998827 DOI: 10.3390/ijms23073606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 12/07/2022] Open
Abstract
Glutathione transferases (GSTs; EC 2.5.1.18) form a group of multifunctional enzymes that are involved in phase II of the cellular detoxification mechanism and are associated with increased susceptibility to cancer development and resistance to anticancer drugs. The present study aims to evaluate the ligandability of the human GSTM1-1 isoenzyme (hGSTM1-1) using a broad range of structurally diverse pesticides as probes. The results revealed that hGSTM1-1, compared to other classes of GSTs, displays limited ligandability and ligand-binding promiscuity, as revealed by kinetic inhibition studies. Among all tested pesticides, the carbamate insecticide pirimicarb was identified as the strongest inhibitor towards hGSTM1-1. Kinetic inhibition analysis showed that pirimicarb behaved as a mixed-type inhibitor toward glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). To shine a light on the restricted hGSTM1-1 ligand-binding promiscuity, the ligand-free crystal structure of hGSTM1-1 was determined by X-ray crystallography at 1.59 Å-resolution. Comparative analysis of ligand-free structure with the available ligand-bound structures allowed for the study of the enzyme's plasticity and the induced-fit mechanism operated by hGSTM1-1. The results revealed important structural features of the H-site that contribute to xenobiotic-ligand binding and specificity. It was concluded that hGSTM1-1 interacts preferentially with one-ring aromatic compounds that bind at a discrete site which partially overlaps with the xenobiotic substrate binding site (H-site). The results of the study form a basis for the rational design of new drugs targeting hGSTM1-1.
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Affiliation(s)
- Charoutioun S Bodourian
- Laboratory of Enzyme Technology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 75 Iera Odos Street, 118 55 Athina, Greece
| | - Nirmal Poudel
- Turku Bioscience Centre, University of Turku and Åbo Akademi University, 20521 Turku, Finland
| | | | - Mariana Antoniadi
- Laboratory of Enzyme Technology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 75 Iera Odos Street, 118 55 Athina, Greece
| | - Nikolaos D Georgakis
- Laboratory of Enzyme Technology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 75 Iera Odos Street, 118 55 Athina, Greece
| | - Hiroshi Abe
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Nikolaos E Labrou
- Laboratory of Enzyme Technology, Department of Biotechnology, School of Applied Biology and Biotechnology, Agricultural University of Athens, 75 Iera Odos Street, 118 55 Athina, Greece
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2
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Uno Y, Murayama N, Tamura K, Yamazaki H. Functionally relevant genetic variants of glutathione S-transferase GSTM5 in cynomolgus and rhesus macaques. Xenobiotica 2018; 49:995-1000. [DOI: 10.1080/00498254.2018.1524187] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Yasuhiro Uno
- Pharmacokinetics and Bioanalysis Center, Shin Nippon Biomedical Laboratories, Ltd, Kainan, Japan
| | - Norie Murayama
- Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, Machida, Japan
| | - Kazuaki Tamura
- Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, Machida, Japan
| | - Hiroshi Yamazaki
- Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, Machida, Japan
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3
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Quesada-Soriano I, Barón C, García-Maroto F, Aguilera AM, García-Fuentes L. Calorimetric Studies of Ligands Binding to Glutathione S-Transferase from the Malarial Parasite Plasmodium falciparum. Biochemistry 2013; 52:1980-9. [DOI: 10.1021/bi400007g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Indalecio Quesada-Soriano
- Department
of Chemistry and Physics, University of Almerı́a, Agrifood Campus of International
Excellence (ceiA3), Ctra de Sacramento s/n, 04120 Almerı́a,
Spain
| | - Carmen Barón
- Department
of Chemistry and Physics, University of Almerı́a, Agrifood Campus of International
Excellence (ceiA3), Ctra de Sacramento s/n, 04120 Almerı́a,
Spain
| | - Federico García-Maroto
- Department
of Chemistry and Physics, University of Almerı́a, Agrifood Campus of International
Excellence (ceiA3), Ctra de Sacramento s/n, 04120 Almerı́a,
Spain
| | - Ana M. Aguilera
- Department
of Chemistry and Physics, University of Almerı́a, Agrifood Campus of International
Excellence (ceiA3), Ctra de Sacramento s/n, 04120 Almerı́a,
Spain
| | - Luís García-Fuentes
- Department
of Chemistry and Physics, University of Almerı́a, Agrifood Campus of International
Excellence (ceiA3), Ctra de Sacramento s/n, 04120 Almerı́a,
Spain
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4
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Zhang X, Li T, Zhang J, Li D, Guo Y, Qin G, Zhu KY, Ma E, Zhang J. Structural and catalytic role of two conserved tyrosines in Delta-class glutathione S-transferase from Locusta migratoria. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2012; 80:77-91. [PMID: 22581614 DOI: 10.1002/arch.21025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Glutathione S-transferases (GSTs) are an important family of detoxifying enzymes and play a key role in pesticide resistance in the insect. Tyrosine is essential for its detoxification function. In the present study, two conserved tyrosine residues are located at positions 108 and 116 in H-site of LmGSTD1. To elucidate how the two residues participate in the catalytic process and keeping structural stability, four mutants, Y108A, Y108E, Y116A, and Y116E, were generated. It was found that the four mutants affected the specific activity of LmGSTD1 in various degrees, depending on the types of substrate and reaction mechanism. Steady-state kinetics assay revealed that Y108E and Y116E had a significant influence on GSH-binding ability, which indicates the two tyrosine residues of H-site contribute to topology rearrangement of G-site. Both Y116A and Y116E exhibited lower CDNB-binding affinity, suggesting that Y116 takes part in hydrophobic substrate binding. The thermostability assay, intrinsic, and 8-anilino-1-naphthalenesulfonic acid (ANS) florescence results showed that the two tyrosine residues were involved in regulation of active-site conformation. Finally, homology modeling provided evidence that the two tyrosines in H-site participate in hydrophobic substrate binding. Furthermore, Y108 is closer to the S atom of S-hexylglutathione. In conclusion, the two tyrosines in LmGSTD1 are important residues in both the catalytic process and protein stability.
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Affiliation(s)
- Xueyao Zhang
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, China
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5
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Bhat VT, Caniard AM, Luksch T, Brenk R, Campopiano DJ, Greaney MF. Nucleophilic catalysis of acylhydrazone equilibration for protein-directed dynamic covalent chemistry. Nat Chem 2010; 2:490-7. [PMID: 20489719 PMCID: PMC2913121 DOI: 10.1038/nchem.658] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 03/30/2010] [Indexed: 12/25/2022]
Abstract
Dynamic covalent chemistry uses reversible chemical reactions to set up an equilibrating network of molecules at thermodynamic equilibrium, which can adjust its composition in response to any agent capable of altering the free energy of the system. When the target is a biological macromolecule, such as a protein, the process corresponds to the protein directing the synthesis of its own best ligand. Here, we demonstrate that reversible acylhydrazone formation is an effective chemistry for biological dynamic combinatorial library formation. In the presence of aniline as a nucleophilic catalyst, dynamic combinatorial libraries equilibrate rapidly at pH 6.2, are fully reversible, and may be switched on or off by means of a change in pH. We have interfaced these hydrazone dynamic combinatorial libraries with two isozymes from the glutathione S-transferase class of enzyme, and observed divergent amplification effects, where each protein selects the best-fitting hydrazone for the hydrophobic region of its active site.
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Affiliation(s)
- Venugopal T. Bhat
- EastChem, School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Anne M. Caniard
- EastChem, School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Torsten Luksch
- College of Life Sciences, University of Dundee, James Black Centre, Dow Street, Dundee DD1 5EH, UK
| | - Ruth Brenk
- College of Life Sciences, University of Dundee, James Black Centre, Dow Street, Dundee DD1 5EH, UK
| | - Dominic J. Campopiano
- EastChem, School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK
| | - Michael F. Greaney
- EastChem, School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK
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6
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Lerksuthirat T, Ketterman AJ. Characterization of putative hydrophobic substrate binding site residues of a Delta class glutathione transferase from Anopheles dirus. Arch Biochem Biophys 2008; 479:97-103. [DOI: 10.1016/j.abb.2008.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 08/07/2008] [Accepted: 08/08/2008] [Indexed: 10/21/2022]
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7
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Baiocco P, Gourlay LJ, Angelucci F, Fontaine J, Hervé M, Miele AE, Trottein F, Brunori M, Bellelli A. Probing the Mechanism of GSH Activation in Schistosoma haematobium Glutathione-S-transferase by Site-directed Mutagenesis and X-ray Crystallography. J Mol Biol 2006; 360:678-89. [PMID: 16777141 DOI: 10.1016/j.jmb.2006.05.040] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 05/10/2006] [Accepted: 05/16/2006] [Indexed: 11/17/2022]
Abstract
During turnover, the catalytic tyrosine residue (Tyr10) of the sigma class Schistosoma haematobium wild-type glutathione-S-transferase is expected to switch alternately in and out of the reduced glutathione-binding site (G-site). The Tyrout10 conformer forms a pi-cation interaction with the guanidinium group of Arg21. As in other similar glutathione-S-transferases, the catalytic Tyr has a low pKa of 7.2. In order to investigate the catalytic role of Tyr10, and the structural and functional roles of Arg21, we carried out structural studies on two Arg21 mutants (R21L and R21Q) and a Tyr10 mutant, Y10F. Our crystallographic data for the two Arg21 mutants indicate that only the Tyrout10 conformation is populated, thereby excluding a role of Arg21 in the stabilisation of the out conformation. However, Arg21 was confirmed to be catalytically important and essential for the low pKa of Tyr10. Upon comparison with structural data generated for reduced glutathione-bound and inhibitor-bound wild-type enzymes, it was observed that the orientations of Tyr10 and Arg35 are concerted and that, upon ligand binding, minor rearrangements occur within conserved residues in the active site loop. These rearrangements are coupled to quaternary rigid-body movements at the dimer interface and alterations in the localisation and structural order of the C-terminal domain.
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Affiliation(s)
- Paola Baiocco
- Department of Biochemical Sciences A. Rossi Fanelli and Istituto Pasteur- Fondazione Cenci Bolognetti, University of Rome La Sapienza, Rome, Italy
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8
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Hiller N, Fritz-Wolf K, Deponte M, Wende W, Zimmermann H, Becker K. Plasmodium falciparum glutathione S-transferase--structural and mechanistic studies on ligand binding and enzyme inhibition. Protein Sci 2005; 15:281-9. [PMID: 16385005 PMCID: PMC2242455 DOI: 10.1110/ps.051891106] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Glutathione S-transferase of the malarial parasite Plasmodium falciparum (PfGST) represents a novel class of GST isoenzymes. Since the architecture of the PfGST substrate binding site differs significantly from its human counterparts and there is only this one isoenzyme present in the parasite, PfGST is considered a highly attractive target for antimalarial drug development. Here we report the mechanistic, kinetic, and structural characterization of PfGST as well as its interaction with different ligands. Our data indicate that in solution PfGST is present as a tetramer that dissociates into dimers in the presence of glutathione (GSH). Fluorescence spectroscopy shows that in the presence of GSH GST serves as ligandin for parasitotoxic ferriprotoporphyrin IX with a high- and a low-affinity binding site. This is supported by a clear uncompetitive inhibition type. Site-directed mutagenesis studies demonstrate that neither Cys 86 nor Cys 101 contribute to the peroxidase activity of the enzyme, which is thus performed GSH-dependently at the active site. Tyr 9 is responsible for the deprotonation of GSH and Lys 15, but also Gln 71 are involved in GSH binding. We furthermore report the 2.4 A resolution X-ray structure of PfGST cocrystallized with the inhibitor S-hexylglutathione. In comparison with a previously reported structure obtained by crystal soaking, differences occur at the C-terminal end of helix alpha4 and at the S-hexylmoiety of the inhibitor. We furthermore show that, in contrast to previous reports, the antimalarial drug artemisinin is not metabolized by PfGST.
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Affiliation(s)
- Nicole Hiller
- Interdisciplinary Research Center, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
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9
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Encío I, Morré DJ, Villar R, Gil MJ, Martínez-Merino V. Benzo[b]thiophenesulphonamide 1,1-dioxide derivatives inhibit tNOX activity in a redox state-dependent manner. Br J Cancer 2005; 92:690-5. [PMID: 15685230 PMCID: PMC2361890 DOI: 10.1038/sj.bjc.6602383] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Benzo[b]thiophenesulphonamide 1,1-dioxide (BTS) derivatives are strong cytotoxic agents that induce reactive oxygen species (ROS) overproduction and apoptosis in tumour cells. Although the precise origin of BTS-induced ROS is not known, a clear correlation between their cytotoxic effect and ability to inhibit a tumour-associated NADH oxidase (tNOX) activity of the plasma membrane has been described. To analyse the putative implication of tNOX in BTS-induced ROS generation, in this work we have synthesised and tested a new BTS derivative, the 6-[N-(2-phenylethyl)]benzo[b]thiophenesulphonamide 1,1-dioxide. According to its high lipophilicity, this compound showed a strong cytotoxic activity against a panel of six human tumour cell lines, including two human leukaemia (K-562 and CCRF-CEM) and four human solid tumours (HT-29, HTB54, HeLa and MEL-AC). We also tested the ability of this compound to inhibit the tNOX activity and we found an absolute dependence of this inhibition on the redox state of the tNOX: while under reducing conditions, that is, 100 mM GSH, the drug inhibits strongly the NOX activity with an EC50 of about 0.1 nM, under oxidising conditions, there is no effect of the drug or just a slight stimulation of activity.
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Affiliation(s)
- I Encío
- Department of Health Sciences, Universidad Pública de Navarra, Avda. Barañain, 31008 Pamplona, Spain
| | - D J Morré
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - R Villar
- Department of Applied Chemistry, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
| | - M J Gil
- Department of Applied Chemistry, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
| | - V Martínez-Merino
- Department of Applied Chemistry, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
- Department of Applied Chemistry, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain. E-mail:
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10
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Haliloglu T, Keskin O, Ma B, Nussinov R. How similar are protein folding and protein binding nuclei? Examination of vibrational motions of energy hot spots and conserved residues. Biophys J 2005; 88:1552-9. [PMID: 15596504 PMCID: PMC1305212 DOI: 10.1529/biophysj.104.051342] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2004] [Accepted: 11/24/2004] [Indexed: 11/18/2022] Open
Abstract
The underlying physico-chemical principles of the interactions between domains in protein folding are similar to those between protein molecules in binding. Here we show that conserved residues and experimental hot spots at intermolecular binding interfaces overlap residues that vibrate with high frequencies. Similarly, conserved residues and hot spots are found in protein cores and are also observed to vibrate with high frequencies. In both cases, these residues contribute significantly to the stability. Hence, these observations validate the proposition that binding and folding are similar processes. In both packing plays a critical role, rationalizing the residue conservation and the experimental alanine scanning hot spots. We further show that high-frequency vibrating residues distinguish between protein binding sites and the remainder of the protein surface.
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Affiliation(s)
- Turkan Haliloglu
- Polymer Research Center and Department of Chemical Engineering, Bogazici University, Bebek 34342, Istanbul, Turkey.
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11
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Villar R, Encio I, Migliaccio M, Gil MJ, Martinez-Merino V. Synthesis and cytotoxic activity of lipophilic sulphonamide derivatives of the benzo[ b ]thiophene 1,1-dioxide. Bioorg Med Chem 2004; 12:963-8. [PMID: 14980609 DOI: 10.1016/j.bmc.2003.12.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2003] [Accepted: 12/12/2003] [Indexed: 10/26/2022]
Abstract
In the search of new compounds with antineoplastic activity, we have analysed the effect of several structural modifications on the nucleus 6-benzo[b]thiophenesulphonamide 1,1-dioxide on its cytotoxic activity on tumour cells. Lipophilic substituents on the sulphonamide group significantly increased the cytotoxic activity measured using a panel of human tumour cell lines. Only slight variations on cytotoxicity were obtained when the sulphonamide group occupied the position 5 of the system. The most active compound was the N-4-methoxyphenyl derivative 15, which showed GI(50) values of 1-9 nM against HT-29, CCRF-CEM, K-562 and MEL-AC cells and of 200 nM against HTB-54 cells. Free access to the 3-position of the heterocyclic system seems to be required to obtain cytotoxic derivatives. Derivative 15 was also active at the same level of commercial Doxorubicine against cultured normal human lung fibroblasts.
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Affiliation(s)
- R Villar
- Dpto. de Química, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
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12
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Fritz-Wolf K, Becker A, Rahlfs S, Harwaldt P, Schirmer RH, Kabsch W, Becker K. X-ray structure of glutathione S-transferase from the malarial parasite Plasmodium falciparum. Proc Natl Acad Sci U S A 2003; 100:13821-6. [PMID: 14623980 PMCID: PMC283505 DOI: 10.1073/pnas.2333763100] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GSTs catalyze the conjugation of glutathione with a wide variety of hydrophobic compounds, generally resulting in nontoxic products that can be readily eliminated. In contrast to many other organisms, the malarial parasite Plasmodium falciparum possesses only one GST isoenzyme (PfGST). This GST is highly abundant in the parasite, its activity was found to be increased in chloroquine-resistant cells, and it has been shown to act as a ligandin for parasitotoxic hemin. Thus, the enzyme represents a promising target for antimalarial drug development. We now have solved the crystal structure of PfGST at a resolution of 1.9 A. The homodimeric protein of 26 kDa per subunit represents a GST form that cannot be assigned to any of the known GST classes. In comparison to other GSTs, and, in particular, to the human isoforms, PfGST possesses a shorter C-terminal section resulting in a more solvent-accessible binding site for the hydrophobic and amphiphilic substrates. The structure furthermore reveals features in this region that could be exploited for the design of specific PfGST inhibitors.
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Affiliation(s)
- Karin Fritz-Wolf
- Department of Biophysics, Max Planck Institute for Medical Research, D-69120 Heidelberg, Germany.
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13
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Wongsantichon J, Harnnoi T, Ketterman AJ. A sensitive core region in the structure of glutathione S-transferases. Biochem J 2003; 373:759-65. [PMID: 12708968 PMCID: PMC1223525 DOI: 10.1042/bj20030394] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2003] [Revised: 04/11/2003] [Accepted: 04/23/2003] [Indexed: 11/17/2022]
Abstract
A variant form of an Anopheles dirus glutathione S-transferase (GST), designated AdGSTD4-4, possesses a single amino acid change of leucine to arginine (Leu-103-Arg). Although residue 103 is outside of the active site, it has major effects on enzymic properties. To investigate these structural effects, site-directed mutagenesis was used to generate mutants by changing the non-polar leucine to alanine, glutamate, isoleucine, methionine, asparagine, or tyrosine. All of the recombinant GSTs showed approximately the same expression level at 25 degrees C. Several of the mutants lacked glutathione (GSH)-binding affinity but were purified by S-hexyl-GSH-based affinity chromatography. However the protein yields (70-fold lower), as well as the GST activity (100-fold lower), of Leu-103-Tyr and Leu-103-Arg purifications were surprisingly low and precluded the performance of kinetic experiments. Size-exclusion chromatography showed that both GSTs Leu-103-Tyr and Leu-103-Arg formed dimers. Using 1-chloro-2,4-dinitrobenzene (CDNB) and GSH substrates to determine kinetic constants it was demonstrated that the other Leu-103 mutants possessed a greater K (m) towards GSH and a differing K (m) towards CDNB. The V (max) ranged from 44.7 to 87.0 micromol/min per mg (wild-type, 44.7 micromol/min per mg). Substrate-specificity studies showed different selectivity properties for each mutant. The structural residue Leu-103 affects the active site through H-bond and van-der-Waal contacts with six active-site residues in the GSH binding site. Changes in this interior core residue appear to disrupt internal packing, which affects active-site residues as well as residues at the subunit-subunit interface. Finally, the data suggest that Leu-103 is noteworthy as a sensitive residue in the GST structure that modulates enzyme activity as well as stability.
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Affiliation(s)
- Jantana Wongsantichon
- Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, Nakhon Pathom 73170, Thailand
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