Structural differences between oxidized and reduced thioredoxin monitored by two-dimensional 1H NMR spectroscopy.

Two-dimensional high resolution NMR techniques have been applied to study the structural differences between the oxidized and reduced forms of Escherichia coli thioredoxin in solution. Sequential proton resonance assignments indicate only limited conformational changes; major chemical shift differences are found for a few residues in a beta-strand immediately preceding the active site S-S bridge and the active site itself. Additional resonance shifts are observed for several residues distant in the primary sequence. The X-ray structure of oxidized thioredoxin shows that these residues form a flat hydrophobic surface, close to the active site S-S bridge, which is probably involved in interactions with other protein molecules.