Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa.
Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa.
Mol Biochem Parasitol. 2020 Nov;240:111319. doi: 10.1016/j.molbiopara.2020.111319. Epub 2020 Sep 19.
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 IC 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-NH of the γ-glutamyl moiety of GSH, in each subunit.
日本血吸虫谷胱甘肽 S-转移酶（Sj26GST）是一种在寄生虫中解毒亲电化合物的关键酶，它会对药物治疗产生上调反应。因此，Sj26GST 可能成为治疗血吸虫病的潜在治疗靶点。在此，我们描述了鞣花酸（EA）抑制 Sj26GST 的结构基础。使用 1-氯-2,4-二硝基苯和还原型谷胱甘肽（GSH）作为 Sj26GST 的底物，EA 对 Sj26GST 活性的抑制作用为 66%，IC 为 2.4 μM。荧光光谱表明，EA 改变了内源性色氨酸环境的极性，并且 EA 降低（剂量依赖性）了 Sj26GST 与 8-苯胺-1-萘磺酸（ANS）之间的相互作用，ANS 是 GST H 位配体。热力学研究表明，Sj26GST 与 EA 之间的相互作用是自发的（ΔG = -29.88 ± 0.07 kJ/mol），由焓驱动（ΔH = -9.48 ± 0.42 kJ/mol），伴有有利的熵变（ΔS = 20.40 ± 0.08 kJ/mol/K），每个 Sj26GST 二聚体结合四个 EA 分子。分辨率为 1.53 Å 的 Sj26GST 晶体结构（P 21 21 21 空间群）与 GSH 和 EA 复合物表明，EA 主要结合在二聚体界面上，主要由范德华力和氢键稳定。此外，EA 结合在 H 位附近，并且距离每个亚基中 GSH 的 γ-谷氨酰部分的 ε-NH 小于 3.5 Å。
