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Thermodynamics of the ligandin function of human class Alpha glutathione transferase A1-1: energetics of organic anion ligand binding

2002; Portland Press; Volume: 363; Issue: 2 Linguagem: Inglês

10.1042/0264-6021

1470-8728

Yasien Sayed, Judith A. T. Hornby, Marimar LOPEZ, Heini W. Dirr,

Drug Transport and Resistance Mechanisms

In addition to their catalytic functions, cytosolic glutathione S-transferases (GSTs) are a major reserve of high-capacity binding proteins for a large variety of physiological and exogenous non-substrate compounds.This ligandin function has implicated GSTs in numerous ligand-uptake, -transport and -storage processes.The binding of non-substrate ligands to GSTs can inhibit catalysis.In the present study, the energetics of the binding of the non-substrate ligand 8-anilino-1-naphthalene sulphonate (ANS) to wild-type human class Alpha GST with two type-1 subunits (hGSTA1-1) and its ∆Phe-222 deletion mutant were studied by isothermal titration calorimetry.The stoichiometry of binding to both proteins is one ANS molecule per GST subunit with a Abbreviations used : A-LBP, adipose lipid-binding protein ; ANS, 8-anilino-1-naphthalene sulphonate ; ASA, solvent-accessible surface area ; GST, glutathione S-transferase ; hGSTA1-1, human class Alpha GST with two type-1 subunits ; ∆Phe-222, deletion of Phe-222 from the C-terminus of hGSTA1-1 ; I-FABP, intestinal fatty acid-binding protein ; ITC, isothermal titration calorimetry ; ∆C p , heat-capacity change.