Discovery of a Ferredoxin:NAD+‐Oxidoreductase (Rnf) in Acetobacterium woodii

Acetogens use the Wood–Ljungdahl pathway for reduction of carbon dioxide to acetate. This pathway not only allows reoxidation of reducing equivalents during heterotrophic growth but also supports chemolithoautotrophic growth on H2 + CO2. The latter argues for this pathway being a source for net energy conservation, but the mechanism involved remains unknown. In addition to CO2, acetogens can use alternative electron acceptors, such as nitrate or caffeate. Caffeate respiration in the model acetogen Acetobacterium woodii is coupled to energy conservation via a chemiosmotic mechanism, with Na+ as coupling ion. The pathway and its bioenergetics were solved in some detail very recently. This review focuses on the regulation of caffeate respiration, describes the enyzmes involved, summarizes the evidence for a potential Na+‐translocating ferredoxin:NAD+‐oxidoreductase (Rnf complex) as a new coupling site, and hypothesizes on the role of this Rnf complex in the Wood–Ljungdahl pathway.

[1]  L. Ljungdahl,et al.  The Acetyl-CoA Pathway and the Chemiosmotic Generation of ATP during Acetogenesis , 1994 .

[2]  M. Saier,et al.  Phylogenetic characterization of the ubiquitous electron transfer flavoprotein families ETF-α and ETF-β , 1995 .

[3]  F. Rudolph,et al.  Cloning, sequencing, and expression of clustered genes encoding beta-hydroxybutyryl-coenzyme A (CoA) dehydrogenase, crotonase, and butyryl-CoA dehydrogenase from Clostridium acetobutylicum ATCC 824 , 1996, Journal of bacteriology.

[4]  M. Verkhovsky,et al.  Na+-translocating NADH: Quinone oxidoreductase: Progress achieved and prospects of investigations , 2005, Biochemistry (Moscow).

[5]  G. Diekert,et al.  Metabolism of homoacetogens , 2004, Antonie van Leeuwenhoek.

[6]  H. König,et al.  Occurrence of corrinoid-containing membrane proteins in anaerobic bacteria , 1987, Archives of Microbiology.

[7]  G. Gottschalk,et al.  The Sodium Ion Cycle in Acetogenic and Methanogenic Bacteria: Generation and Utilization of a Primary Electrochemical Sodium Ion Gradient , 1994 .

[8]  R. Hedderich.  Energy-Converting [NiFe] Hydrogenases from Archaea and Extremophiles: Ancestors of Complex I , 2004, Journal of bioenergetics and biomembranes.

[9]  G. Butler,et al.  Cloning and Analysis of the Genes for a Novel Electron-transferring Flavoprotein from Megasphaera elsdenii , 1998, The Journal of Biological Chemistry.

[10]  P. Rich,et al.  Predicted structure and possible ionmotive mechanism of the sodium‐linked NADH‐ubiquinone oxidoreductase of Vibrio alginolyticus , 1995, FEBS letters.

[11]  R. Thauer,et al.  Energy Conservation in Chemotrophic Anaerobic Bacteria , 1977, Bacteriological reviews.

[12]  R. Komuniecki,et al.  Electron-transfer flavoprotein from anaerobic Ascaris suum mitochondria and its role in NADH-dependent 2-methyl branched-chain enoyl-CoA reduction. , 1989, Biochimica et biophysica acta.

[13]  P. Dimroth,et al.  NADH:ubiquinone oxidoreductase of Vibrio alginolyticus: purification, properties, and reconstitution of the Na+ pump. , 1996, Biochemistry.

[14]  V. Müller,et al.  Chemiosmotic Energy Conservation with Na+ as the Coupling Ion during Hydrogen-Dependent Caffeate Reduction by Acetobacterium woodii , 2002, Journal of bacteriology.

[15]  S. Ragsdale,et al.  Hydrogenase from Acetobacterium woodii , 1984, Archives of Microbiology.

[16]  N. Pfennig,et al.  Growth yield increase linked to caffeate reduction in Acetobacterium woodii , 1984, Archives of Microbiology.

[17]  T. Unemoto,et al.  A respiration-dependent primary sodium extrusion system functioning at alkaline pH in the marine bacterium Vibrio alginolyticus. , 1981, Biochemical and biophysical research communications.

[18]  V. Müller,et al.  Molecular and cellular biology of acetogenic bacteria , 2004 .

[19]  J. Oelze,et al.  Identification of a new class of nitrogen fixation genes in Rhodobacter capsalatus: a putative membrane complex involved in electron transport to nitrogenase , 1993, Molecular and General Genetics MGG.

[20]  N. Pfennig,et al.  Selective isolation of Acetobacterium woodii on methoxylated aromatic acids and determination of growth yields , 1981, Archives of Microbiology.

[21]  Qingbo Li,et al.  Electron Transport in the Pathway of Acetate Conversion to Methane in the Marine Archaeon Methanosarcina acetivorans , 2006, Journal of bacteriology.

[22]  G. Gottschalk,et al.  The Na(+)-translocating methyltransferase complex from methanogenic archaea. , 2001, Biochimica et biophysica acta.

[23]  R. Thauer,et al.  Energy conservation in chemotrophic anaerobic bacteria , 1977, Bacteriological reviews.

[24]  J. Willison,et al.  Overexpression in Escherichia coli of the rnf genes from Rhodobacter capsulatus--characterization of two membrane-bound iron-sulfur proteins. , 1998, European journal of biochemistry.

[25]  V. Müller,et al.  Dissection of the Caffeate Respiratory Chain in the Acetogen Acetobacterium woodii: Identification of an Rnf-Type NADH Dehydrogenase as a Potential Coupling Site , 2007, Journal of bacteriology.

[26]  B. Golding,et al.  Acryloyl-CoA reductase from Clostridium propionicum. An enzyme complex of propionyl-CoA dehydrogenase and electron-transferring flavoprotein. , 2003, European journal of biochemistry.

[28]  R. Hedderich,et al.  Sodium Ion Pumps and Hydrogen Production in Glutamate Fermenting Anaerobic Bacteria , 2006, Journal of Molecular Microbiology and Biotechnology.

[29]  V. Müller,et al.  Regulation of Caffeate Respiration in the Acetogenic Bacterium Acetobacterium woodii , 2007, Applied and Environmental Microbiology.

[30]  H. Matsubara,et al.  Membrane localization, topology, and mutual stabilization of the rnfABC gene products in Rhodobacter capsulatus and implications for a new family of energy-coupling NADH oxidoreductases. , 1997, Biochemistry.

[31]  P. Schönheit,et al.  ATP formation coupled to caffeate reduction by H2 in Acetobacterium woodii NZva16 , 1988, Archives of Microbiology.

[32]  J. Steuber.  Na(+) translocation by bacterial NADH:quinone oxidoreductases: an extension to the complex-I family of primary redox pumps. , 2001, Biochimica et biophysica acta.

[33]  Anamitra Bhattacharyya,et al.  The genome of Syntrophus aciditrophicus: Life at the thermodynamic limit of microbial growth , 2007, Proceedings of the National Academy of Sciences.

[34]  D. J. Steenkamp,et al.  Reactions of electron-transfer flavoprotein and electron-transfer flavoprotein: ubiquinone oxidoreductase. , 1987, The Biochemical journal.

[35]  Rainer Merkl,et al.  The genome sequence of Clostridium tetani, the causative agent of tetanus disease , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[36]  M. Kikuchi,et al.  Characterization and Transcription of the Genes Involved in Butyrate Production in Butyrivibrio fibrisolvens TypeI and II Strains , 2005, Current Microbiology.

[37]  L. Curatti,et al.  Genes required for rapid expression of nitrogenase activity in Azotobacter vinelandii. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[38]  G. Gottschalk,et al.  Bioenergetics of Methanogenesis , 1993 .

[39]  F. Frerman.  Reaction of electron-transfer flavoprotein ubiquinone oxidoreductase with the mitochondrial respiratory chain. , 1987, Biochimica et biophysica acta.

[40]  Harold L. Drake,et al.  Acetogenesis: Reality in the Laboratory, Uncertainty Elsewhere , 1994 .

[41]  V. Müller,et al.  Energy Conservation in Acetogenic Bacteria , 2003, Applied and Environmental Microbiology.