Thermodynamic aspects of DsbD-mediated electron transport.
DsbD from Escherichia coli transports electrons from cytoplasmic thioredoxin across the inner membrane to the periplasmic substrate proteins DsbC, DsbG and CcmG. DsbD consists of three domains: a periplasmic N-terminal domain, a central transmembrane domain (tmDsbD) and a periplasmic C-terminal domain. Each domain contains two essential cysteine residues that are required for electron transport. In contrast to the quinone reductase DsbB, HPLC analysis of the methanol/hexane extracts of purified DsbD revealed no presence of quinones, suggesting that the tmDsbD interacts with thioredoxin and the periplasmic C-terminal domain exclusively via disulfide exchange. We also demonstrate that a DsbD variant containing only the redox-active cysteine pair C163 and C285 in tmDsbD, reconstituted into liposomes, has a redox potential of -0.246 V. The results show that all steps in the DsbD-mediated electron flow are thermodynamically favorable.
Rozhkova
Anna
A
Institute of Molecular Biology and Biophysics, ETH Zurich, CH-8093 Zurich, Switzerland. annarozhkova@hotmail.com
Glockshuber
Rudi
R
D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019897:Periplasm / Q000737:chemistry; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D013879:Thioredoxins / Q000378:metabolism
D004220:Disulfides; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D013879:Thioredoxins; D010088:Oxidoreductases; C094848:DsbD electron transport protein, E coli