Crd. Lancaster, Succinate : quinone oxidoreductases - what can we learn from Wolinella succinogenes quinol : fumarate reductase?, FEBS LETTER, 504(3), 2001, pp. 133-141
The structure of Wolinella succinogenes quinol:fumarate reductase by X-ray
crystallography has been determined at 2.2-Angstrom resolution [Lancaster e
t al. (1999), Nature 402, 377-385]. Based on the structure of the three pro
tein 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 cytochrom
e b in the membrane to the site of fumarate reduction in the hydrophilic su
bunit A has been proposed. By combining the results from site-directed muta
genesis, functional and electrochemical characterisation, and X-ray crystal
lography, a residue was identified which is essential for menaquinol oxidat
ion. [Lancaster et al. (2000), Proc. Natl. Acad. Sci. USA 97, 13051-13056].
The location of this residue in the structure suggests that the coupling o
f the oxidation of menaquinol to the reduction of fumarate in dihaem-contai
ning succinate:quinone oxidoreductases could be associated with the generat
ion of a transmembrane electrochemical potential. Based on crystallographic
analysis of three different crystal forms of the enzyme and the results fr
om site-directed mutagenesis, we have derived a mechanism of fumarate reduc
tion 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. (C) 2001 Federation of European Bioch
emical Societies. Published by Elsevier Science B.V. All rights reserved.