Crystallographic and Thermodynamic Analysis of the Binding of S-Octylglutathione to the Tyr 7 to Phe Mutant of Glutathione S-Transferase from Schistosoma japonicum

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• 作者：Montserrat Andú ; jar-S&aacute ; nchez ; Alex W. Smith ; Josefa Marí ; a Clemente-Jimenez ; Felipe Rodriguez-Vico ; Francisco Javier Las Heras-Vazquez ; Vicente Jara-Pé ; rez ; and Ana C&aacute ; ma
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：February 1, 2005
• 年：2005
• 卷：44
• 期：4
• 页码：1174 - 1183
• 全文大小：310K
• 年卷期：v.44,no.4(February 1, 2005)
• ISSN：1520-4995

文摘

Glutathione S-transferases are a family of multifunctional enzymes involved in the metabolismof drugs and xenobiotics. Two tyrosine residues, Tyr 7 and Tyr 111, in the active site of the enzyme playan important role in the binding and catalysis of substrate ligands. The crystal structures of Schistosomajaponicum glutathione S-transferase tyrosine 7 to phenylalanine mutant [SjGST(Y7F)] in complex withthe substrate glutathione (GSH) and the competitive inhibitor S-octylglutathione (S-octyl-GSH) have beenobtained. These new structural data combined with fluorescence spectroscopy and thermodynamic data,obtained by means of isothermal titration calorimetry, allow for detailed characterization of the ligand-binding process. The binding of S-octyl-GSH to SjGST(Y7F) is enthalpically and entropically driven attemperatures below 30 s/entities/deg.gif">C. The stoichiometry of the binding is one molecule of S-octyl-GSH per mutantdimer, whereas shorter alkyl derivatives bind with a stoichiometry of two molecules per mutant dimer.The SjGST(Y7F)·GSH structure showed no major structural differences compared to the wild-type enzyme.In contrast, the structure of SjGST(Y7F)·S-octyl-GSH showed asymmetric binding of S-octyl-GSH. Thislack of symmetry is reflected in the lower symmetry space group of the SjGST(Y7F)·S-octyl-GSH crystals(P6₃) compared to that of the SjGST(Y7F)·GSH crystals (P6₃22). Moreover, the binding of S-octyl-GSHto the A subunit is accompanied by conformational changes that may be responsible for the lack of bindingto the B subunit.