Intrinsic fluorescence quenching of glutathione transferase pi by glutathione binding.

A M Caccuri, A Aceto, N Rosato, C Di Ilio, F Piemonte, G Federici

Index: Ital. J. Biochem. 40(5) , 304-11, (1991)

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Abstract

The binding of the GSH to the GSH transferase pi quenches the protein intrinsic fluorescence more than the binding of GS-Me. The calculated dissociation constants are 38.6 microM and 90.9 microM for GSH and GS-Me, respectively. From the reported data it is evident that the binding of GSH to GSH transferase pi quenches the intrinsic fluorescence with two different mechanisms. The first one is a conformational change induced by the binding of the GSH and it is present also with the GS-Me binding. A second proposed mechanism is a contact quenching between the sulphydryl GSH group and a tryptophan residue. This suggests that at least one of the tryptophan residues is located near the GSH binding site.