title: Complex II from phototrophic purple bacterium Rhodoferax fermentans displays rhodoquinol-fumarate reductase activity.
abstract: It has long been accepted that bacterial quinol-fumarate reductase (QFR) generally uses a low-redox-potential naphthoquinone, menaquinone (MK), as the electron donor, whereas mitochondrial QFR from facultative and anaerobic eukaryotes uses a low-redox-potential benzoquinone, rhodoquinone (RQ), as the substrate. In the present study, we purified novel complex II from the RQ-containing phototrophic purple bacterium, Rhodoferax fermentans that exhibited high rhodoquinol-fumarate reductase activity in addition to succinate-ubiquinone reductase activity. SDS/PAGE indicated that the purified R. fermentans complex II comprises four subunits of 64.0, 28.6, 18.7 and 17.5 kDa and contains 1.3 nmol heme per mg protein. Phylogenetic analysis and comparison of the deduced amino acid sequences of R. fermentans complex II with pro/eukaryotic complex II indicate that the structure and the evolutional origins of R. fermentans complex II are closer to bacterial SQR than to mitochondrial rhodoquinol-fumarate reductase. The results strongly indicate that R. fermentans complex II and mitochondrial QFR might have evolved independently, although they both utilize RQ for fumarate reduction.
authors.affiliation: Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Miyadera
authors.forename: Akira
authors.initials: A
authors.lastname: Hiraishi
authors.forename: Hideto
authors.initials: H
authors.lastname: Miyoshi
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Reiko
authors.initials: R
authors.lastname: Mineki
authors.forename: Kimie
authors.initials: K
authors.lastname: Murayama
authors.forename: Kenji V P
authors.initials: KV
authors.lastname: Nagashima
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsuura
authors.forename: Somei
authors.initials: S
authors.lastname: Kojima
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020562:Betaproteobacteria / Q000145:classification / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D002848:Chromatography, DEAE-Cellulose; D017124:Conserved Sequence; D042963:Electron Transport Complex II; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010802:Phylogeny; D021122:Protein Subunits / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013385:Succinate Dehydrogenase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D021122:Protein Subunits; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase