title: Energy Conservation Model Based on Genomic and Experimental Analyses of a Carbon Monoxide-Utilizing, Butyrate-Forming Acetogen, Eubacterium limosum KIST612.
abstract: Eubacterium limosum KIST612 is one of the few acetogens that can produce butyrate from carbon monoxide. We have used a genome-guided analysis to delineate the path of butyrate formation, the enzymes involved, and the potential coupling to ATP synthesis. Oxidation of CO is catalyzed by the acetyl-coenzyme A (CoA) synthase/CO dehydrogenase and coupled to the reduction of ferredoxin. Oxidation of reduced ferredoxin is catalyzed by the Rnf complex and Na(+) dependent. Consistent with the finding of a Na(+)-dependent Rnf complex is the presence of a conserved Na(+)-binding motif in the c subunit of the ATP synthase. Butyrate formation is from acetyl-CoA via acetoacetyl-CoA, hydroxybutyryl-CoA, crotonyl-CoA, and butyryl-CoA and is consistent with the finding of a gene cluster that encodes the enzymes for this pathway. The activity of the butyryl-CoA dehydrogenase was demonstrated. Reduction of crotonyl-CoA to butyryl-CoA with NADH as the reductant was coupled to reduction of ferredoxin. We postulate that the butyryl-CoA dehydrogenase uses flavin-based electron bifurcation to reduce ferredoxin, which is consistent with the finding of etfA and etfB genes next to it. The overall ATP yield was calculated and is significantly higher than the one obtained with H2 + CO2. The energetic benefit may be one reason that butyrate is formed only from CO but not from H2 + CO2.
authors.affiliation: School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Jiyeong
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Frankfurt, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Bertsch
authors.affiliation: Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Frankfurt, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Hess
authors.affiliation: School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Sunju
authors.initials: S
authors.lastname: Choi
authors.affiliation: Computational and Synthetic Biology Laboratory, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea.
authors.forename: In-Geol
authors.initials: IG
authors.lastname: Choi
authors.affiliation: School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea ischang@gist.ac.kr vmueller@bio.uni-frankfurt.de.
authors.forename: In Seop
authors.initials: IS
authors.lastname: Chang
authors.affiliation: Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Frankfurt, Germany ischang@gist.ac.kr vmueller@bio.uni-frankfurt.de.
authors.forename: Volker
authors.initials: V
authors.lastname: Müller
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002087:Butyrates / Q000378:metabolism*; D044926:Butyryl-CoA Dehydrogenase / Q000235:genetics / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism*; D004734:Energy Metabolism; D005051:Eubacterium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005415:Flavins / Q000378:metabolism; D023281:Genomics; D010084:Oxidation-Reduction
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; D002087:Butyrates; D005415:Flavins; C024343:butyryl-coenzyme A; D002248:Carbon Monoxide; D000255:Adenosine Triphosphate; C010701:crotonyl-coenzyme A; D044926:Butyryl-CoA Dehydrogenase