title: Characterization of the binding of 8-anilinonaphthalene sulfonate to rat class Mu GST M1-1.
abstract: Molecular docking and ANS-displacement experiments indicated that 8-anilinonaphthalene sulfonate (ANS) binds the hydrophobic site (H-site) in the active site of dimeric class Mu rGST M1-1. The naphthalene moiety provides most of the van der Waals contacts at the ANS-binding interface while the anilino group is able to sample different rotamers. The energetics of ANS binding were studied by isothermal titration calorimetry (ITC) over the temperature range of 5-30 degrees C. Binding is both enthalpically and entropically driven and displays a stoichiometry of one ANS molecule per subunit (or H-site). ANS binding is linked to the uptake of 0.5 protons at pH 6.5. Enthalpy of binding depends linearly upon temperature yielding a DeltaC(p) of -80+/-4 cal K(-1) mol(-1) indicating the burial of solvent-exposed nonpolar surface area upon ANS-protein complex formation. While ion-pair interactions between the sulfonate moiety of ANS and protein cationic groups may be significant for other ANS-binding proteins, the binding of ANS to rGST M1-1 is primarily hydrophobic in origin. The binding properties are compared with those of other GSTs and ANS-binding proteins.
authors.affiliation: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Wiwatersrand, Johannesburg 2050, South Africa.
authors.forename: Nichole
authors.initials: N
authors.lastname: Kinsley
authors.forename: Yasien
authors.initials: Y
authors.lastname: Sayed
authors.forename: Salerwe
authors.initials: S
authors.lastname: Mosebi
authors.forename: Richard N
authors.initials: RN
authors.lastname: Armstrong
authors.forename: Heini W
authors.initials: HW
authors.lastname: Dirr
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002151:Calorimetry; D003198:Computer Simulation; D004976:Ethacrynic Acid / Q000737:chemistry; D005978:Glutathione / Q000031:analogs & derivatives / Q000737:chemistry; D005982:Glutathione Transferase / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D000817:Anilino Naphthalenesulfonates; D004976:Ethacrynic Acid; D005978:Glutathione; D005982:Glutathione Transferase; D011994:Recombinant Proteins; C515594:8-anilino-1-naphthalenesulfonic acid; C040136:glutathione sulfonate