||The enzyme is very similar to EC 220.127.116.11, succinate dehydrogenase, but differs by containing two heme molecules (located in the membrane anchor component) in addition to FAD and three iron-sulfur clusters. Unlike EC 18.104.22.168, this enzyme catalyses an electrogenic reaction, enabled by electron-bifurcation via the heme molecules. In the direction of succinate oxidation by menaquinone, which is endergonic, the reaction is driven by the transmembrane electrochemical proton potential. In the direction of fumarate reduction, the electrogenic electron transfer reaction is compensated by transmembrane proton transfer pathway known as the E-pathway, which results in overall electroneutrality.
||Lancaster, C.R. Wolinella succinogenes quinol:fumarate reductase-2.2-A resolution crystal structure and the E-pathway hypothesis of coupled transmembrane proton and electron transfer. Biochim. Biophys. Acta 1565 (2002) 215–231. [DOI] [PMID: 12409197]
||Madej, M.G., Nasiri, H.R., Hilgendorff, N.S., Schwalbe, H., Unden, G. and Lancaster, C.R. Experimental evidence for proton motive force-dependent catalysis by the diheme-containing succinate:menaquinone oxidoreductase from the Gram-positive bacterium Bacillus licheniformis. Biochemistry 45 (2006) 15049–15055. [DOI] [PMID: 17154542]
||Lancaster, C.R., Herzog, E., Juhnke, H.D., Madej, M.G., Muller, F.G., Paul, R. and Schleidt, P.G. Electroneutral and electrogenic catalysis by dihaem-containing succinate:quinone oxidoreductases. Biochem Soc Trans. 36 (2008) 996–1000. [DOI] [PMID: 18793177]
||Lancaster, C.R. The di-heme family of respiratory complex II enzymes. Biochim. Biophys. Acta 1827 (2013) 679–687. [DOI] [PMID: 23466335]
||Guan, H.H., Hsieh, Y.C., Lin, P.J., Huang, Y.C., Yoshimura, M., Chen, L.Y., Chen, S.K., Chuankhayan, P., Lin, C.C., Chen, N.C., Nakagawa, A., Chan, S.I. and Chen, C.J. Structural insights into the electron/proton transfer pathways in the quinol:fumarate reductase from Desulfovibrio gigas. Sci. Rep. 8:14935 (2018). [DOI] [PMID: 30297797]