title: 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.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboã, Oeiras, Portugal.
authors.forename: Rita S
authors.initials: RS
authors.lastname: Lemos
authors.forename: Andreia S
authors.initials: AS
authors.lastname: Fernandes
authors.forename: Manuela M
authors.initials: MM
authors.lastname: Pereira
authors.forename: Cláudio M
authors.initials: CM
authors.lastname: Gomes
authors.forename: Miguel
authors.initials: M
authors.lastname: Teixeira
mesh_terms: D000595:Amino Acid Sequence; D042963:Electron Transport Complex II; D005420:Flavoproteins / Q000737:chemistry; D005650:Fumarates / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D011808:Quinone Reductases / Q000737:chemistry / Q000145:classification / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013385:Succinate Dehydrogenase / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D019802:Succinic Acid / Q000737:chemistry
chemical_list: D005420:Flavoproteins; D005650:Fumarates; D007506:Iron-Sulfur Proteins; D008670:Metals; D009097:Multienzyme Complexes; D006418:Heme; C032005:fumaric acid; D019802:Succinic Acid; D010088:Oxidoreductases; D042963:Electron Transport Complex II; C424907:quinol fumarate reductase; D013385:Succinate Dehydrogenase; D011808:Quinone Reductases; C073412:sulfide quinone reductase