Bacterial growth and pathogenicity depend on the correct formation of disulfide bonds, a process controlled by the Dsb system in the periplasm of Gram-negative bacteria. Proteins with a thioredoxin fold play a central role in this process. A general feature of thiol:disulfide exchange reactions is the need to avoid a long-lived product complex between protein partners. We use a multi-disciplinary approach, involving NMR, X-ray crystallography, surface plasmon resonance, mutagenesis and in vivo experiments, to investigate the interaction between the two soluble domains of the transmembrane reductant conductor DsbD. Our results show oxidation-state-dependent affinities between these two domains. These observations have implications for the interactions of the ubiquitous thioredoxin-like proteins with their substrates, provide insight into the key role played by a unique redox partner with an immunoglobulin fold, and are of general importance for oxidative protein-folding pathways in all organisms.
The article is published online in the Journal of Biological Chemistry and is free to access.