Publications

• F420H2: quinone oxidoreductase from Archaeoglobus fulgidus. Characterization of a membrane-bound multisubunit complex containing FAD and iron-sulfur clusters.

  Kunow J., Linder D., Stetter K.O., Thauer R.K.

  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 w ... >> More

  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. << Less

  Eur J Biochem 223:503-511(1994) [PubMed] [EuropePMC]

• Structure of the F420H2:quinone oxidoreductase of Archaeoglobus fulgidus identification and overproduction of the F420H2-oxidizing subunit.

  Bruggemann H., Falinski F., Deppenmeier U.

  The F420H2:quinone oxidoreductase from the sulfate-reducing archaeon Archaeoglobus fulgidus is encoded by the fqo gene cluster which comprises 11 genes (fqo J, K, M, L, N, A, BC, D, H, I, F). The last gene of the cluster, fqoF, was overexpressed in Escherichia coli. The purified subunit was able t ... >> More

  The F420H2:quinone oxidoreductase from the sulfate-reducing archaeon Archaeoglobus fulgidus is encoded by the fqo gene cluster which comprises 11 genes (fqo J, K, M, L, N, A, BC, D, H, I, F). The last gene of the cluster, fqoF, was overexpressed in Escherichia coli. The purified subunit was able to oxidize reduced cofactor F420 using the electron-acceptor system methyl viologen plus metronidazole. The specific activity at 78 degrees C was 64 micromol F420H2 oxidized. min-1.(mg protein)-1. The purified polypeptide contained 10.6 mol non-heme iron, 7.2 mol acid-labile sulfur and 0.7 mol FAD per mol protein. With the exception of fqoF, the deduced amino-acid sequences of all other genes show homologies to distinct subunits of NADH-quinone oxidoreductases from prokaryotes and eukaryotes. Thus, it is concluded that the F420H2-dependent and the NADH-dependent enzyme are functional equivalents. Both proteins are the initial enzymes of membrane-bound electron-transport systems and are involved in energy conservation. In parallel with bacterial complex I, the F420H2:quinone oxidoreductase may be composed of three subcomplexes. FqoF functions as the input device adjusted to the oxidation of reduced cofactor F420H2, thereby replacing subunits of the input module of complex I that are not present in A. fulgidus. The subunits FqoB, FqoCD and FqoI may form the membrane-associated module and transfer electrons to the membrane-integral module. It is most likely that the last subcomplex is composed of FqoA, FqoH, FqoJ, FqoK, FqoL, FqoM and FqoN. All subunits are highly hydrophobic and are probably involved in the reduction of a special menaquinone with a fully reduced isoprenoid side chain present in the cytoplasmic membrane of A. fulgidus. << Less

  Eur J Biochem 267:5810-5814(2000) [PubMed] [EuropePMC]