Succinate:quinone oxidoreductases--what can we learn from Wolinella succinogenes quinol:fumarate reductase?
The structure of Wolinella succinogenes quinol:fumarate reductase by X-ray crystallography has been determined at 2.2-A resolution [Lancaster et al. (1999), Nature 402, 377-385]. Based on the structure of the three protein subunits A, B, and C and the arrangement of the six prosthetic groups (a covalently bound FAD, three iron-sulphur clusters, and two haem b groups) a pathway of electron transfer from the quinol-oxidising dihaem cytochrome b in the membrane to the site of fumarate reduction in the hydrophilic subunit A has been proposed. By combining the results from site-directed mutagenesis, functional and electrochemical characterisation, and X-ray crystallography, a residue was identified which is essential for menaquinol oxidation. [Lancaster et al. (2000), Proc. Natl. Acad. Sci. USA 97, 13051-13056]. The location of this residue in the structure suggests that the coupling of the oxidation of menaquinol to the reduction of fumarate in dihaem-containing succinate:quinone oxidoreductases could be associated with the generation of a transmembrane electrochemical potential. Based on crystallographic analysis of three different crystal forms of the enzyme and the results from site-directed mutagenesis, we have derived a mechanism of fumarate reduction and succinate oxidation [Lancaster et al. (2001) Eur. J. Biochem. 268, 1820-1827], which should be generally relevant throughout the superfamily of succinate:quinone oxidoreductases.
Lancaster
C R
CR
Max-Planck-Institut für Biophysik, Abteilung Molekulare Membranbiologie, Heinrich-Hoffmann-Str. 7, D-60528, Frankfurt am Main, Germany. roy.lancaster@mpibp-frankfurt.mpg.de
D002462:Cell Membrane / Q000201:enzymology; D018360:Crystallography, X-Ray; D004579:Electron Transport; D042963:Electron Transport Complex II; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D010088:Oxidoreductases / Q000737:chemistry* / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D011522:Protons; D013385:Succinate Dehydrogenase / Q000737:chemistry* / Q000502:physiology*; D016968:Wolinella / Q000201:enzymology*
D009097:Multienzyme Complexes; D011522:Protons; D010088:Oxidoreductases; D042963:Electron Transport Complex II; C424907:quinol fumarate reductase; D013385:Succinate Dehydrogenase; D010100:Oxygen