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 sulphonate (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 °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 ΔC 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.

A thermodynamic characterization of the interaction of 8‐anilino‐1‐naphthalenesulfonic acid with native globular proteins: the effect of the ligand dimerization in the analysis of the binding isotherms

“…However, the enthalpy of binding obtained at this pH is negative, which cannot be explained in terms of a classical hydrophobic effect. This negative value for the binding enthalpy of ANS has been also observed in other proteins (Kinsley et al, 2008). To explain this negative value, we may bear in mind that in this case the hydrophobic effect has been modified by the presence of charge effects, due to the negative charge of the sulfonate.…”

“…This technique provides us a full thermodynamic description of the process and also allows us to complete the information obtained by means of other techniques. Thus, in addition to the fluorescence studies, ITC experiments have been used to evaluate the binding of ANS to proteins (Matulis and Lovrien, 1998;Celej et al, 2005;Banerjee and Kishore, 2006;Singh and Kishore, 2006;Kinsley et al, 2008). In these studies, the binding isotherms obtained at acidic pH values show a complex behavior and their analysis is not always possible (Sharma and Kishore, 2009).…”

Thermodynamic study of the dimerization of 8-anilino-1-naphthalenesulfonic acid by isothermal titration calorimetry

“…To study the nature of the forces responsible for the binding of ANS, the energetics of the interaction ANS-protein has been studied for different proteins by isothermal titration calorimetry [16,[18][19][20][21][22][23]. In all these works, the thermograms are corrected with the dilution heat of ANS obtained in blank experiments injecting the dye into buffer.…”

Survey of the year 2008: applications of isothermal titration calorimetry

“…In 2008, we identified more than 500 articles after searching Web of Science, PubMed, SciDir and OVID databases using ‘isothermal AND titration AND calorimetry’ or ITC or ‘Isothermal Titration Calorimetry’ search terms. Following the format of previous annual surveys these have been classified into the following categories: References cited in the text and review articles 1–82. Protein–protein and protein–peptide interactions 83–222. Protein–small ligand or protein–drug interactions 223–321. Protein/peptide metal interactions 322–355. Protein/peptide nucleic acid interactions 356–387. Protein/peptide lipid interactions …”