scholarly journals Evidence of reversed electron transport in syntrophic butyrate or benzoate oxidation by Syntrophomonas wolfei and Syntrophus buswellii

1994 ◽  
Vol 162 (1-2) ◽  
pp. 136-142 ◽  
Author(s):  
Christina Wallrabenstein ◽  
Bernhard Schink
Keyword(s):  
Electron Transport ◽  
Syntrophomonas Wolfei ◽  
Reversed Electron Transport

scholarly journals Involvement of NADH:Acceptor Oxidoreductase and Butyryl Coenzyme A Dehydrogenase in Reversed Electron Transport during Syntrophic Butyrate Oxidation by Syntrophomonas wolfei

2009 ◽  
Vol 191 (19) ◽  
pp. 6167-6177 ◽  
Author(s):  
Nicolai Müller ◽  
David Schleheck ◽  
Bernhard Schink
Keyword(s):  
Electron Transport ◽  
Coenzyme A ◽  
Peptide Mass Fingerprinting ◽  
Exchange Chromatography ◽  
Triphenyltetrazolium Chloride ◽  
Oxidoreductase Activity ◽  
Cell Extracts ◽  
Peptide Mass ◽  
Syntrophomonas Wolfei ◽  
Reversed Electron Transport

ABSTRACT Methanogenic oxidation of butyrate to acetate requires a tight cooperation between the syntrophically fermenting Syntrophomonas wolfei and the methanogen Methanospirillum hungatei, and a reversed electron transport system in S. wolfei was postulated to shift electrons from butyryl coenzyme A (butyryl-CoA) oxidation to the redox potential of NADH for H2 generation. The metabolic activity of butyrate-oxidizing S. wolfei cells was measured via production of formazan and acetate from butyrate, with 2,3,5-triphenyltetrazolium chloride as electron acceptor. This activity was inhibited by trifluoperazine (TPZ), an antitubercular agent known to inhibit NADH:menaquinone oxidoreductase. In cell extracts of S. wolfei, the oxidation of NADH could be measured with quinones, viologens, and tetrazolium dyes as electron acceptors, and also this activity was inhibited by TPZ. The TPZ-sensitive NADH:acceptor oxidoreductase activity appeared to be membrane associated but could be dissociated from the membrane as a soluble protein and was semipurified by anion-exchange chromatography. Recovered proteins were identified by peptide mass fingerprinting, which indicated the presence of an NADH:acceptor oxidoreductase as part of a three-component [FeFe] hydrogenase complex and a selenocysteine-containing formate dehydrogenase. Furthermore, purification of butyryl-CoA dehydrogenase (Bcd) activity and peptide mass fingerprinting revealed two Bcd proteins different from the Bcd subunit of the Bcd/electron-transfer flavoprotein complex (Bcd/EtfAB) predicted from the genome sequence of S. wolfei. The results suggest that syntrophic oxidation of butyrate in S. wolfei involves a membrane-associated TPZ-sensitive NADH:acceptor oxidoreductase as part of a hydrogenase complex similar to the recently discovered “bifurcating” hydrogenase in Thermotoga maritima and butyryl-CoA dehydrogenases that are different from Bcd of the Bcd/EtfAB complex.

Mitochondrial superoxide and aging: uncoupling-protein activity and superoxide production

2004 ◽  
Vol 71 ◽  
pp. 203-213 ◽  
Author(s):  
Martin D. Brand ◽  
Julie A. Buckingham ◽  
Telma C. Esteves ◽  
Katherine Green ◽  
Adrian J. Lambert ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Electron Transport ◽  
Complex I ◽  
Uncoupling Protein ◽  
Proton Motive Force ◽  
Motive Force ◽  
Superoxide Production ◽  
Lipid Peroxidation Product ◽  
Mild Uncoupling ◽  
Reversed Electron Transport

Mitochondria are a major source of superoxide, formed by the one-electron reduction of oxygen during electron transport. Superoxide initiates oxidative damage to phospholipids, proteins and nucleic acids. This damage may be a major cause of degenerative disease and aging. In isolated mitochondria, superoxide production on the matrix side of the membrane is particularly high during reversed electron transport to complex I driven by oxidation of succinate or glycerol 3-phosphate. Reversed electron transport and superoxide production from complex I are very sensitive to proton motive force, and can be strongly decreased by mild uncoupling of oxidative phosphorylation. Both matrix superoxide and the lipid peroxidation product 4-hydroxy-trans-2-nonenal can activate uncoupling through endogenous UCPs (uncoupling proteins). We suggest that superoxide releases iron from aconitase, leading to a cascade of lipid peroxidation and the release of molecules such as hydroxy-nonenal that covalently modify and activate the proton conductance of UCPs and other proteins. A function of the UCPs may be to cause mild uncoupling in response to matrix superoxide and other oxidants, leading to lowered proton motive force and decreased superoxide production. This simple feedback loop would constitute a self-limiting cycle to protect against excessive superoxide production, leading to protection against aging, but at the cost of a small elevation of respiration and basal metabolic rate.

Role of reversed electron transport in bovine corpus luteum mitochondrial steroid synthesis

Biochemistry ◽  
1971 ◽  
Vol 10 (15) ◽  
pp. 2916-2923 ◽  
Author(s):  
V. I. Uzgiris ◽  
E. N. McIntosh ◽  
C. Alonso ◽  
H. A. Salhanick
Keyword(s):  
Electron Transport ◽  
Corpus Luteum ◽  
Steroid Synthesis ◽  
Bovine Corpus Luteum ◽  
Reversed Electron Transport

The role of ligands in electron transport in nanocrystal solids

Nanoscale ◽  
2020 ◽  
Vol 12 (45) ◽  
pp. 23028-23035
Author(s):  
Artem R. Khabibullin ◽  
Alexander L. Efros ◽  
Steven C. Erwin
Keyword(s):  
Electron Transport ◽  
Theoretical Modeling

Theoretical modeling of wavefunction overlap in nanocrystal solids elucidates the important role played by ligands in electron transport.

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