title: A novel five-subunit-type 2-oxoglutalate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus TK-6.
abstract: A thermophilic, chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, fixes carbon dioxide via the reductive TCA cycle. 2-Oxoglutarate:ferredoxin oxidoreductase (OGOR) of this strain is one of the key enzymes of the pathway. OGOR of strain TK-6 has been reported to be a two-subunit-type OGOR and encoded by korAB. A gene cluster, forDABGEF, encoding another OGOR was found 148 bp upstream of korAB in the opposite orientation. Five of the for genes (forDABGE) were required for the expression of the active recombinant enzyme in Escherichia coli. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed five polypeptides corresponding to the forDABGE gene products, suggesting that the enzyme had a novel five-subunit structure. The recombinant enzyme had high substrate specificity toward 2-oxoglutarate as in the case of the gene products of korAB. Primer extension analysis showed that the korA and forD genes were transcribed from one and two transcriptional initiation sites, respectively. The results also suggested that both gene clusters were expressed in the cells of strain TK-6.
authors.affiliation: Department of Biotechnology, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Na-Rae
authors.initials: NR
authors.lastname: Yun
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D001420:Bacteria, Aerobic / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D021122:Protein Subunits; D013379:Substrate Specificity; D024363:Transcription Initiation Site; D014170:Transformation, Genetic
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D007658:Ketone Oxidoreductases; C023096:2-oxoglutarate synthase