title: Salt influence on glutathione--Schistosoma japonicum glutathione S-transferase binding.
abstract: There has been some speculation about the salt independence of Schistosoma japonicum glutathione S-transferase (Sj26GST, EC. 2.5.1.18), but this aspect has not been carefully studied before. To establish the basis for a further development of this dependence, we have performed a methodical study of the influence of some important ions and their concentration on the binding properties of glutathione to Sj26GST by means of isothermal calorimetry and fluorescence quenching. Salts like NaCl, Na(2)SO(4) and MgSO(4) do not change practically the affinity of the protein for its substrate, whilst MgCl(2) has the effect of decreasing the affinity as its concentration rises. However, the enthalpy change is not affected by all the salts studied, and so, the entropy change is the causal factor in dropping the affinity. We also looked at the conformational stability of the protein under different conditions to check the structural changes they provide, and found that the unfolding parameters are practically not affected by the salt concentration. We discuss the results in terms of the chaotropic nature of the ions implied.
authors.affiliation: Dpto. de Química Física, Bioquímica y Q. Inorgánica, Facultad de Ciencias Experimentales, Universidad de Almería, La Cañada de San Urbano, 04120 Almeria, Spain.
authors.forename: Zeyad
authors.initials: Z
authors.lastname: Yassin
authors.forename: M José
authors.initials: MJ
authors.lastname: Clemente-Jiménez
authors.forename: Ramiro
authors.initials: R
authors.lastname: Téllez-Sanz
authors.forename: Luis
authors.initials: L
authors.lastname: García-Fuentes
mesh_terms: D000818:Animals; D002151:Calorimetry; D002851:Chromatography, High Pressure Liquid; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D012492:Salts / Q000494:pharmacology*; D012549:Schistosoma japonicum / Q000201:enzymology*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics; D014508:Urea / Q000494:pharmacology
chemical_list: D012492:Salts; D014508:Urea; D005982:Glutathione Transferase; D005978:Glutathione