Reactivity of the human thioltransferase (glutaredoxin) C7S, C25S, C78S, C82S mutant and NMR solution structure of its glutathionyl mixed disulfide intermediate reflect catalytic specificity

The molecular aspects of human thioltransferase specificity for the glutathione moiety were investigated. A quadruple Cys to Ser mutant of human thioltransferase, namely, C7S, C25S, C78S and C82S, was derived. Experimental results showed that the disulfide-adducted glutathione in the thioltransferase-S-S-glutathione complex has an extended conformation and is localized in a cleft near the protein surface containing the residues from helices-alpha2, alpha3, the active site loop and the loop linking helix-alpha3 and strand-beta3.