To test thioredoxin resistance to oxidizing free radicals, we have studied the one-electron oxidation of wild-type thio-redoxin and of two forms with the point mutations D30A and W35A, using azide radicals generated byc-ray or pulse radiolysis. The oxidation patterns of wild-type thioredoxin and D30A are similar. In these forms, Trp35 is the primary target and is repaired by one-electron reduction; first by intramolecular electron transfer from tyrosine, and then fromother residues. Conversely, duringoxidationofW35A, Trp13 is poorly reactive. For all proteins, activity is con-served showing an unusual resistance toward oxidation
