Yeast thiol-dependent protector protein expression enhances the resistance of Escherichia coli to hydrogen peroxide.

A soluble protein from Saccharomyces cerevisiae specifically provides protection against a thiol-containing oxidation system but not against an oxidation system without thiol. This 25-kDa protein was thus named thiol-dependent protector protein (TPP). The role of TPP in the cellular defense against oxidative stress was investigated in Escherichia coli containing an expression vector with a yeast genomic DNA fragment that encodes TPP (strain YP) and mutants in which the catalytically essential amino acid cysteine (Cys-47) has been replaced with alanine (strain YPC47A) or tryptophan (Trp-82) has been replaced with phenylalanine (strain YPW82F) by a site directed mutagenesis. There was a distinct difference between these three strains in regards to growth inhibition kinetics, viability, modulation of activities of superoxide dismutase and catalase, and the accumulation of oxidized proteins. These results suggest that TPP may play a direct role in the cellular defense against oxidative stress by functioning as an antioxidant protein.