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Biochim Biophys Acta. 2002 Jan 17;1553(1-2):158-70.

Quinol:fumarate oxidoreductases and succinate:quinone oxidoreductases: phylogenetic relationships, metal centres and membrane attachment.

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Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboã, Oeiras, Portugal.


A comprehensive phylogenetic analysis of the core subunits of succinate:quinone oxidoreductases and quinol:fumarate oxidoreductases is performed, showing that the classification of the enzymes as type A to E based on the type of the membrane anchor fully correlates with the specific characteristics of the two core subunits. A special emphasis is given to the type E enzymes, which have an atypical association to the membrane, possibly involving anchor subunits with amphipathic helices. Furthermore, the redox properties of the SQR/QFR proteins are also reviewed, stressing out the recent observation of redox-Bohr effect upon haem reduction, observed for the Desulfovibrio gigas and Rhodothermus marinus enzymes, which indicates a direct protonation event at the haems or at a nearby residue. Finally, the possible contribution of these enzymes to the formation/dissipation of a transmembrane proton gradient is discussed, considering recent experimental and structural data.

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