Anabolic five subunit-type pyruvate:ferredoxin oxidoreductase from Hydrogenobacter thermophilus TK-6

• Published in: Biochemical and biophysical research communications Vol. 340; no. 1; pp. 76 - 82
• Main Authors: Ikeda, Takeshi, Ochiai, Toshihiro, Morita, Susumu, Nishiyama, Ayako, Yamada, Eio, Arai, Hiroyuki, Ishii, Masaharu, Igarashi, Yasuo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03.02.2006
• Subjects: 2-Oxoacid oxidoreductase; 2-Oxoglutarate:ferredoxin oxidoreductase; Amino Acid Sequence; Anabolic Agents - analysis; Anabolic Agents - chemistry; Bacterial Proteins - analysis; Bacterial Proteins - chemistry; Enzyme Activation; Escherichia coli; Hydrogenobacter thermophilus; Molecular Sequence Data; Molecular Weight; Protein Subunits; Pyruvate Synthase - analysis; Pyruvate Synthase - chemistry; Pyruvate:ferredoxin oxidoreductase; Reductive tricarboxylic acid cycle; Thermophile; 2-Oxoglutarate:ferredoxin oxidoreductase; Hydrogenobacter thermophilus; Thermophile; 2-Oxoacid oxidoreductase; Reductive tricarboxylic acid cycle; Pyruvate:ferredoxin oxidoreductase
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2005.11.155

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 α, β, γ, and δ 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.