Intrinsic fluorescence quenching of glutathione transferase pi by glutathione binding
Caccuri, A.M.; Aceto, A.; Rosato, N.; Di Ilio, C.; Piemonte, F.; Federici, G.
Italian Journal of Biochemistry 40(5): 304-311
1991
ISSN/ISBN: 0021-2938 PMID: 1774154 Document Number: 375622
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 .mu.M and 90.0 .mu.M 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.