Thermodynamics of glutathione binding to the tyrosine 7 to phenylalanine mutant of glutathione S-transferase from Schistosoma japonicum
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Andújar Sánchez, Montserrat; Clemente Jiménez, Josefa María; Las Heras Vázquez, Francisco Javier; Rodríguez Vico, Felipe; Cámara Artigas, Ana María; [et al.]Fecha
2003Resumen
The binding of glutathione (GSH) to the tyrosine 7 to phenylalanine mutant of Schistosoma japonicum glutathione S-transferase
(SjGST-Y7F) has been studied by isothermal titration calorimetry (ITC). At pH 6.5 and 25 ◦C this mutant shows a higher affinity for
glutathione than wild type enzyme despite an almost complete loss of activity in the presence of 1-chloro-2,4-dinitrobenzene (CDNB) as
second substrate. The enthalpy change upon binding of GSH is more negative for the mutant than for the wild type GST (SjGST). Changes
in accessible solvent areas (ASA) have been calculated based on enthalpy and heat capacity changes. ASA values indicated the burial of
apolar surfaces of protein and ligand upon binding. A more negative Cp value has been obtained for the mutant enzyme, suggesting a
more hydrophobic interaction, as may be expected from the change of a tyrosine residue to phenylalanine.
Palabra/s clave
Microcalorimetry
Site-direct mutagenesis
Fluorescence