Role of mutation Y6F on the binding properties of Schistosoma japonicum glutathione S-transferase
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Ortiz Salmerón, Emilia; Clemente Jiménez, Josefa María; Barón Bravo, Carmen Francisca; García Fuentes, Luis; Zeyad EFecha
2003Resumen
The role of the hydroxyl group of tyrosine 6 in the binding of Schistosoma japonicum glutathione S-transferase has been investigated
by isothermal titration calorimetry (ITC). A site-specific replacement of this residue with phenylalanine produces the Y6F mutant, which
shows negative cooperativity for the binding of reduced glutathione (GSH). Calorimetric measurements indicated that the binding of GSH
to Y6F dimer is enthalpically driven over the temperature range investigated. A concomitant net uptake of protons upon binding of GSH to
Y6F mutant was detected carrying out calorimetric experiments in various buffer systems with different heats of ionization. The entropy
change is favorable at temperatures below 26 ◦C for the first site, being entropically favorable at all temperatures studied for the second
site. The enthalpy change of binding is strongly temperature-dependent, arising from a large negative C◦p1= −3.45±0.62 kJK−1 mol−1
for the first site, whereas a small C◦p2= ...
Palabra/s clave
Glutathione S-transferase
Schistosoma japonicum
Glutathione
Unfolding
Fluorescence
Binding
Microcalorimetry
S-Methylglutathione