Naphthoquinone preferentially pairs with non-proton-pumping NADH dehydrogenase for respiratory electron transport
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ABSTRACT:
ORGANISM(S): Escherichia coli
PROVIDER: GSE303520 | GEO | 2025/09/15
REPOSITORIES: GEO
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Project description:Naphthoquinone preferentially pairs with non-proton-pumping NADH dehydrogenase for respiratory electron transport
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Project description: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 H(2) 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.
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2018-08-29 | E-MTAB-5368 | biostudies-arrayexpress
Project description:The objective of this comparison was to identify the impact of NADH on the transcriptome of Streptococcus pneumoniae D39. Transcriptome comparison of the D39 wild-type grown in chemically-defined medium (CDM) with 0 mg/ml NADH to 0.5 mg/ml NADH revealed elevated expression of various genes/operons (adhB1, fba, hemH, rex, gapN, nirC, pncB, gap, adhE, and adhB2) involved in the transport and biosynthesis of niacin. In this study, we investigated the transcriptomic response of Streptococcus pneumoniae D39 to NADH. Transcriptome comparison of the D39 wild-type grown in chemically-defined medium (CDM) with 0 mg/ml NADH to 0.5 mg/ml NADH revealed elevated expression of various genes/operons (adhB1, fba, hemH, rex, gapN, nirC, pncB, gap, adhE, and adhB2) involved in the transport and biosynthesis of niacin. Microarray results were further confirmed by β-galactosidase assays. Promoter-lacZ fusions assays and microarray studies showed that the transcriptional regulator, Rex acts as a transcriptional repressor of a number of genes/operons (adhB1, fba, hemH, rex, gapN, nirC, pncB, gap, adhE, and adhB2) involved in niacin uptake and biosynthesis in the presence of NADH. The putative operator site of Rex in the promoter regions of Rex-regulated genes is predicted and confirmed by promoter mutational experiments.
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