title: F420H2: quinone oxidoreductase from Archaeoglobus fulgidus. Characterization of a membrane-bound multisubunit complex containing FAD and iron-sulfur clusters.
abstract: Archaeoglobus fulgidus, a hyperthermophilic sulfate-reducing archaeon, was found to contain a membrane-bound F420H2: quinone oxidoreductase complex presumed to be involved in energy conservation during growth on lactate plus sulfate. After solubilization with dodecyl-beta-D-maltoside the complex was purified 32-fold with a yield of 24%. Using both gel filtration and native PAGE, an apparent molecular mass of approximately 270 kDa was determined. SDS/PAGE revealed the presence of at least seven polypeptides with apparent molecular masses 56, 45, 41, 39, 37, 33, and 32 kDa. The purified complex contained 1.6 mol FAD, 9 mol non-heme iron and 7 mol acid-labile sulfur/mol complex. It did not contain cytochromes, which were, however, present in the membrane fraction of A. fulgidus (3 nmol/mg membrane protein). The purified F420H2: quinone oxidoreductase complex catalyzed the reduction of 2,3-dimethyl-1,4-naphthoquinone (apparent Km 190 microM) with reduced coenzyme F420 (apparent Km 50 microM) exhibiting a specific activity of 500 U/mg (apparent Vmax) at pH 8.0 (pH optimum) and 65 degrees C (temperature optimum). 2-Methyl-1,4-naphthoquinone (menadione), 2-hydroxy-1,4-naphthoquinone, 1,4-naphthoquinone, 2,3-dimethoxy-5-methyl-1,4- benzoquinone, and 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (decyl-ubiquinone) were also reduced with F420H2, albeit with lower rates. The physiological electron acceptor of the F420H2: quinone oxidoreductase complex is most likely the menaquinone found in the membrane fraction of A. fulgidus.
authors.affiliation: Laboratorium für Mikrobiologie des Fachbereichs Biologie, Philipps-Universität, Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Kunow
authors.forename: D
authors.initials: D
authors.lastname: Linder
authors.forename: K O
authors.initials: KO
authors.lastname: Stetter
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology* / Q000254:growth & development; D002384:Catalysis; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003580:Cytochromes / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D008667:Metalloproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D009285:Naphthoquinones / Q000378:metabolism; D019159:Nonheme Iron Proteins; D011808:Quinone Reductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012256:Riboflavin / Q000031:analogs & derivatives / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism
chemical_list: D003580:Cytochromes; D008667:Metalloproteins; D009097:Multienzyme Complexes; D009285:Naphthoquinones; D019159:Nonheme Iron Proteins; D005182:Flavin-Adenine Dinucleotide; C041498:2,3-dimethyl-1,4-naphthoquinone; C015084:coenzyme F420; D013455:Sulfur; D007501:Iron; C088764:coenzyme F420H2 - 2,3-dimethyl-1,4-naphthoquinone oxidoreductase; D011808:Quinone Reductases; D012256:Riboflavin