The Role of Lipophilic Quinones in the Electron Transport System of Escherichia Coli*.

1964 ◽  
Vol 55 (4) ◽  
pp. 432-445 ◽  
Author(s):  
Eiji Itagaki
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Transport System ◽  
Electron Transport System

scholarly journals PdhR (Pyruvate Dehydrogenase Complex Regulator) Controls the Respiratory Electron Transport System in Escherichia coli

2007 ◽  
Vol 189 (15) ◽  
pp. 5534-5541 ◽  
Author(s):  
Hiroshi Ogasawara ◽  
Yuji Ishida ◽  
Kayoko Yamada ◽  
Kaneyoshi Yamamoto ◽  
Akira Ishihama
Keyword(s):  
Escherichia Coli ◽  
Electron Transport ◽  
Transport System ◽  
Pyruvate Dehydrogenase ◽  
Fluorescent Protein ◽  
Pyruvate Dehydrogenase Complex ◽  
Consensus Sequence ◽  
Electron Transport System ◽  
Respiratory Electron Transport

ABSTRACT The pyruvate dehydrogenase (PDH) multienzyme complex plays a key role in the metabolic interconnection between glycolysis and the citric acid cycle. Transcription of the Escherichia coli genes for all three components of the PDH complex in the pdhR-aceEF-lpdA operon is repressed by the pyruvate-sensing PdhR, a GntR family transcription regulator, and derepressed by pyruvate. After a systematic search for the regulation targets of PdhR using genomic systematic evolution of ligands by exponential enrichment (SELEX), we have identified two novel targets, ndh, encoding NADH dehydrogenase II, and cyoABCDE, encoding the cytochrome bo-type oxidase, both together forming the pathway of respiratory electron transport downstream from the PDH cycle. PDH generates NADH, while Ndh and CyoABCDE together transport electrons from NADH to oxygen. Using gel shift and DNase I footprinting assays, the PdhR-binding site (PdhR box) was defined, which includes a palindromic consensus sequence, ATTGGTNNNACCAAT. The binding in vitro of PdhR to the PdhR box decreased in the presence of pyruvate. Promoter assays in vivo using a two-fluorescent-protein vector also indicated that the newly identified operons are repressed by PdhR and derepressed by the addition of pyruvate. Taken together, we propose that PdhR is a master regulator for controlling the formation of not only the PDH complex but also the respiratory electron transport system.

scholarly journals Human blood contains circulating cell-free mitochondria, but are they really functional?

2020 ◽  
Author(s):  
Antoine Stier
Keyword(s):  
Electron Transport ◽  
Transport System ◽  
Human Blood ◽  
Electron Transport System ◽  
Complex Iv ◽  
Mitochondrial Inhibitors ◽  
Functional Part ◽  
Positive Controls

AbstractDache et al. (2020, FASEB J. 15, e2002338–15) recently reported the presence of respiratory-competent cell-free mitochondria in human blood (up to 3.7 x 106 per mL of blood), providing exciting perspectives on the potential role of these extra-cellular mitochondria. While their evidence for the presence of cell-free mitochondria in human blood is compelling, their conclusion that these cell-free mitochondria are respiratory-competent or functional has to be re-evaluated. To this end, we evaluated the functionality of cell-free mitochondria in human blood using high-resolution respirometry and mitochondria extracted from platelets of the same blood samples as positive controls. While cell-free mitochondria were present in human plasma (i.e. significant complex IV activity), there was no evidence suggesting that their mitochondrial electron transport system (ETS) was functional (i.e. respiration rate not significantly different from 0; no significant responses to ADP, uncoupler or mitochondrial inhibitors oligomycin and antimycin A). Yet, in vitro complex IV activity was detectable and even slightly higher than levels found in mitochondria extracted from platelets, suggesting that cell-free mitochondria in human blood only retain a non-functional part of the electron transport system. Despite being unlikely to be fully functional in the narrow-sense (i.e. capable of oxidative phosphorylation), circulating cell-free mitochondria may have significant physiological roles that remain to be elucidated.

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