title: Anabolic five subunit-type pyruvate:ferredoxin oxidoreductase from Hydrogenobacter thermophilus TK-6.
abstract: The thermophilic, obligately chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, assimilates carbon dioxide via the reductive tricarboxylic acid cycle. A gene cluster, porEDABG, encoding pyruvate:ferredoxin oxidoreductase (POR), which plays a key role in this cycle, was cloned and sequenced. The nucleotide sequence and the gene organization were similar to those of the five subunit-type 2-oxoglutarate:ferredoxin oxidoreductase from this strain, although the anabolic POR had been previously reported to consist of four subunits. A small protein (8 kDa) encoded by porE, which had not been detected in the previous work, was identified in the purified recombinant POR expressed in Escherichia coli, indicating that the enzyme is also a five-subunit type. Incorporation of PorE in the wild-type POR enzyme was confirmed by immunological analysis. PorA, PorB, PorG, and PorE were similar to the alpha, beta, gamma, and delta subunits of the four subunit-type 2-oxoacid oxidoreductases, respectively, and had conserved specific motifs. PorD had no specific motifs but was essential for the expression of the active enzyme.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ikeda
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ochiai
authors.forename: Susumu
authors.initials: S
authors.lastname: Morita
authors.forename: Ayako
authors.initials: A
authors.lastname: Nishiyama
authors.forename: Eio
authors.initials: E
authors.lastname: Yamada
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: D000595:Amino Acid Sequence; D045930:Anabolic Agents / Q000032:analysis / Q000737:chemistry; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry*; D004789:Enzyme Activation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D021122:Protein Subunits; D050743:Pyruvate Synthase / Q000032:analysis / Q000737:chemistry*
chemical_list: D045930:Anabolic Agents; D001426:Bacterial Proteins; D021122:Protein Subunits; D050743:Pyruvate Synthase