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

Abstract

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.

Genetic Characterization of a Single Bifunctional Enzyme for Fumarate Reduction and Succinate Oxidation in Geobacter sulfurreducens and Engineering of Fumarate Reduction in Geobacter metallireducens

“…The complete G. sulfurreducens genome (31) was searched with sequences of subunits from each of the different classes of fumarate reductases and succinate dehydrogenases (20). A single putative operon with three open reading frames was identified and designated frdCAB (Fig.…”

“…Four conserved histidines, which have been shown to bind two b-type hemes in W. succinogenes (16), were also identified in the FrdC sequence. The succinate dehydrogenase of the gram-positive aerobe Bacillus subtilis is also a member of this B-type family of enzymes (20), and the G. sulfurreducens FrdCAB proteins are more similar to this enzyme (31% amino acid identity between A subunits) than to the fumarate reductases found in other Proteobacteria, such as W. succinogenes (23%) and H. pylori (20%).…”

Protein Tyrosine Nitration of the Flavin Subunit Is Associated with Oxidative Modification of Mitochondrial Complex II in the Post-ischemic Myocardium

“…Succinate dehydrogenase contains two protein subunits, a 70-kDa protein with a covalently bound FAD, and a 27-kDa iron-sulfur protein hosting S1, S2, and S3 iron-sulfur clusters (21). The membrane-anchoring protein fraction contains cytochrome b hosting two hydrophobic polypeptides (CybL/14 kDa and CybS/9 kDa) with heme b binding (22).…”

Evolution of b-type cytochromes in prokaryotes

“…cyanobacteria and chlorobi end up in groups I and VI, chloroflexi in groups IV and VI, and delta-proteobacteria in groups I, IV and VI. A previous analysis of the soluble subunits of succinate dehydrogenase distinguished five different types of the enzyme (Lemos et al, 2002). Although the trees are difficult to compare, as different species were included in each, in general terms, groups I and VI of our analysis correspond to type E, groups II and III correspond to type C, group IV corresponds to type A, and group V corresponds to type B.…”