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 tho ught to occur through the formation and subsequent destruction of a mi xed-disulfide intermediate between thioredoxin and the substrate. In o rder to model the interaction, we have prepared a mutant of Escherichi a coli thioredoxin where the second cysteine residue of the active sit e has been replaced by an alanine residue.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 co mplex.