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Pooe K, Thulo M, Makumbe H, Akumadu B, Otun O, Aloke C, Achilonu I. Biophysical description of Bromosulfophthalein interaction with the 28-kDa glutathione transferase from Schistosoma japonicum. Mol Biochem Parasitol 2022; 252:111524. [PMID: 36195242 DOI: 10.1016/j.molbiopara.2022.111524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 09/12/2022] [Accepted: 09/29/2022] [Indexed: 12/31/2022]
Abstract
Glutathione transferases (GSTs) are major detoxification enzymes vital for the survival and reproduction of schistosomes during infection in humans. Schistosoma encode two GST isoenzymes, the 26- and 28-kDa isoforms, that show different substrate specificities and cellular localisations. Bromosulfophthalein (BSP) has been identified and characterised as a potent 26-kDa Schistosoma japonicum GST (Sj26GST) inhibitor with an anthelmintic potential. This study describes the structure, function, and ligandin properties of the 28-kDa Schistosoma japonicum GST (Sj28GST) towards BSP. Enzyme kinetics show that BSP is a potent enzyme inhibitor, with a specific activity decreases from 60.4 µmol/min/mg to 0.0742 µmol/min/mg and an IC50 in the micromolar range of 0.74 µM. Far-UV circular dichroism confirmed that purified Sj28GST follows a typical GST fold, which is predominantly alpha-helical. Fluorescence spectroscopy suggests that BSP binding occurs at a site distinct from the glutathione-binding site (G-site); however, the binding does not alter the local G-site environment. Isothermal titration calorimetry studies show that the binding of BSP to Sj28GST is exergonic (∆G°= -33 kJ/mol) and enthalpically-driven, with a stoichiometry of one BSP per dimer. The stability of Sj28GST (∆G(H2O) = 4.7 kcal/mol) is notably lower than Sj26GST, owing to differences in the enzyme's dimeric interfaces. We conclude that Sj28GST shares similar biophysical characteristics with Sj26GST based on its kinetic properties and susceptibility to low concentrations of BSP. The study supports the potential benefits of re-purposing BSP as a potential drug or prodrug to mitigate the scourge of schistosomiasis.
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Affiliation(s)
- Kagiso Pooe
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Monare Thulo
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Hattie Makumbe
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Blessing Akumadu
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Oluwatobin Otun
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Chinyere Aloke
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa.
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Akumadu BO, Pandian R, Olfsen J, Worth R, Thulo M, Mentor T, Fanucchi S, Sayed Y, Dirr HW, Achilonu I. Molecular basis of inhibition of Schistosoma japonicum glutathione transferase by ellagic acid: Insights into biophysical and structural studies. Mol Biochem Parasitol 2020; 240:111319. [PMID: 32961204 DOI: 10.1016/j.molbiopara.2020.111319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 02/06/2023]
Abstract
Schistosoma japonicum glutathione transferase (Sj26GST), an enzyme central to detoxification of electrophilic compounds in the parasite, is upregulated in response to drug treatment. Therefore, Sj26GST may serve as a potential therapeutic target for the treatment of schistosomiasis. Herewith, we describe the structural basis of inhibition of Sj26GST by ellagic acid (EA). Using 1-chloro-2,4-dinitrobenzene and reduced glutathione (GSH) as Sj26GST substrates, EA was shown to inhibit Sj26GST activity by 66 % with an IC50 of 2.4 μM. Fluorescence spectroscopy showed that EA altered the polarity of the environment of intrinsic tryptophan and that EA decreased (in a dose-dependent manner) the interaction between Sj26GST and 8-Anilino-1-naphthalenesulfonate (ANS), which is a known GST H-site ligand. Thermodynamic studies indicated that the interaction between Sj26GST and EA is spontaneous (ΔG = -29.88 ± 0.07 kJ/mol), enthalpically-driven (ΔH = -9.48 ± 0.42 kJ/mol) with a favourable entropic change (ΔS = 20.40 ± 0.08 kJ/mol/K), and with a stoichiometry of four EA molecules bound per Sj26GST dimer. The 1.53 Å-resolution Sj26GST crystal structure (P 21 21 21 space group) complexed with GSH and EA shows that EA binds primarily at the dimer interface, stabilised largely by Van der Waal forces and H-bonding. Besides, EA bound near the H-site and less than 3.5 Å from the ε-NH2 of the γ-glutamyl moiety of GSH, in each subunit.
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Affiliation(s)
- Blessing O Akumadu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ramesh Pandian
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Jessica Olfsen
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Roland Worth
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Monare Thulo
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Tshireletso Mentor
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa.
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