title: Succinate dehydrogenase functioning by a reverse redox loop mechanism and fumarate reductase in sulphate-reducing bacteria.
abstract: Sulphate- or sulphur-reducing bacteria with known or draft genome sequences (Desulfovibrio vulgaris, Desulfovibrio desulfuricans G20, Desulfobacterium autotrophicum [draft], Desulfotalea psychrophila and Geobacter sulfurreducens) all contain sdhCAB or frdCAB gene clusters encoding succinate : quinone oxidoreductases. frdD or sdhD genes are missing. The presence and function of succinate dehydrogenase versus fumarate reductase was studied. Desulfovibrio desulfuricans (strain Essex 6) grew by fumarate respiration or by fumarate disproportionation, and contained fumarate reductase activity. Desulfovibrio vulgaris lacked fumarate respiration and contained succinate dehydrogenase activity. Succinate oxidation by the menaquinone analogue 2,3-dimethyl-1,4-naphthoquinone depended on a proton potential, and the activity was lost after degradation of the proton potential. The membrane anchor SdhC contains four conserved His residues which are known as the ligands for two haem B residues. The properties are very similar to succinate dehydrogenase of the Gram-positive (menaquinone-containing) Bacillus subtilis, which uses a reverse redox loop mechanism in succinate : menaquinone reduction. It is concluded that succinate dehydrogenases from menaquinone-containing bacteria generally require a proton potential to drive the endergonic succinate oxidation. Sequence comparison shows that the SdhC subunit of this type lacks a Glu residue in transmembrane helix IV, which is part of the uncoupling E-pathway in most non-electrogenic FrdABC enzymes.
authors.affiliation: Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg Universität Mainz, 55 099 Mainz, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Zaunmüller
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelly
authors.affiliation: MPI für Marine Mikrobiologie, Celsiusstr. 1, 28359 Bremen, Germany.
authors.forename: Frank O
authors.initials: FO
authors.lastname: Glöckner
authors.affiliation: Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg Universität Mainz, 55 099 Mainz, Germany.
authors.forename: Gottfried
authors.initials: G
authors.lastname: Unden
mesh_terms: D000595:Amino Acid Sequence; D003901:Desulfovibrio / Q000201:enzymology* / Q000235:genetics; D005650:Fumarates / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D010084:Oxidation-Reduction; D013385:Succinate Dehydrogenase / Q000502:physiology*; D019802:Succinic Acid / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*
chemical_list: D005650:Fumarates; D013431:Sulfates; C032005:fumaric acid; D019802:Succinic Acid; D013385:Succinate Dehydrogenase