NMR characterization of a single-cysteine mutant of Escherichia coli thioredoxin and a covalent thioredoxin-peptide complex

The mechanism of disulfide reduction by thioredoxin in the cell is thought to occur through the formation and subsequent destruction of a mixed-disulfide intermediate between thioredoxin and the substrate. In order to model the interaction, we have prepared a mutant of Escherichia coli thioredoxin where the second cysteine residue of the active site has been replaced by an alanine residue. A specific covalent complex has been prepared between the remaining cysteine residue and a short cysteine-containing peptide. This paper describes the preparation and characterization of the mutant protein both free and in the peptide complex.