Redox properties of protein disulfide bonds: Comparison between lysozyme and thioredoxin. A gamma radiolysis study

Thioredoxin is a major oxido-reductase which intervenes in the redox-contro lled cellular signalization pathways. Its active site is a thiol-disulfide function. The study of the one-electron reduction of the oxidized protein b y gamma radiolysis shows that its behaviour is markedly different from that of other protein disulfides, like those of lysozyme. In order to understan d this difference, we have prepared by site-directed mutagenesis two mutant forms of thioredoxin. We observe that the redox properties of the protein are modulated by the amino acids Asp30 and Trp35.