scholarly journals Respiration of Escherichia coli Can Be Fully Uncoupled via the Nonelectrogenic Terminal Cytochrome bd-II Oxidase

2009 ◽  
Vol 191 (17) ◽  
pp. 5510-5517 ◽  
Author(s):  
M. Bekker ◽  
S. de Vries ◽  
A. Ter Beek ◽  
K. J. Hellingwerf ◽  
M. J. Teixeira de Mattos
Keyword(s):  
Escherichia Coli ◽  
Respiratory Chain ◽  
Electron Flux ◽  
Atp Synthesis ◽  
Proton Motive Force ◽  
Proton Pumping ◽  
Motive Force ◽  
Fixed Amount ◽  
Terminal Oxidases ◽  
Genes Encoding

ABSTRACT The respiratory chain of Escherichia coli is usually considered a device to conserve energy via the generation of a proton motive force, which subsequently may drive ATP synthesis by the ATP synthetase. It is known that in this system a fixed amount of ATP per oxygen molecule reduced (P/O ratio) is not synthesized due to alternative NADH dehydrogenases and terminal oxidases with different proton pumping stoichiometries. Here we show that P/O ratios can vary much more than previously thought. First, we show that in wild-type E. coli cytochrome bo, cytochrome bd-I, and cytochrome bd-II are the major terminal oxidases; deletion of all of the genes encoding these enzymes results in a fermentative phenotype in the presence of oxygen. Second, we provide evidence that the electron flux through cytochrome bd-II oxidase is significant but does not contribute to the generation of a proton motive force. The kinetics support the view that this system is as an energy-independent system gives the cell metabolic flexibility by uncoupling catabolism from ATP synthesis under non-steady-state conditions. The nonelectrogenic nature of cytochrome bd-II oxidase implies that the respiratory chain can function in a fully uncoupled mode such that ATP synthesis occurs solely by substrate level phosphorylation. As a consequence, the yield with a carbon and energy source can vary five- to sevenfold depending on the electron flux distribution in the respiratory chain. A full understanding and control of this distribution open new avenues for optimization of biotechnological processes.

scholarly journals Cytochrome bd-II from aerobic respiratory chain of Escherichia coli is a proton-motive force generator

2012 ◽  
Vol 1817 ◽  
pp. S105
Author(s):  
Dmitry A. Bloch ◽  
Vitaliy B. Borisov ◽  
Ranjani Murali ◽  
Marina L. Verkhovskaya ◽  
Huazhi Han ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Respiratory Chain ◽  
Proton Motive Force ◽  
Motive Force ◽  
Cytochrome Bd ◽  
Force Generator

scholarly journals Proton motive force underpins respiration-mediated potentiation of aminoglycoside lethality in pathogenic Escherichia coli

2022 ◽  
Vol 204 (1) ◽  
Author(s):  
Calum M. Webster ◽  
Ayrianna M. Woody ◽  
Safura Fusseini ◽  
Louis G. Holmes ◽  
Gary K. Robinson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Respiratory Chain ◽  
Proton Motive Force ◽  
Motive Force ◽  
Gram Negative Bacteria ◽  
Ros Production ◽  
Gram Negative ◽  
E Coli ◽  
Pathogenic Escherichia Coli ◽  
Aminoglycoside Toxicity

AbstractIt is well known that loss of aerobic respiration in Gram-negative bacteria can diminish the efficacy of a variety of bactericidal antibiotics, which has lead to subsequent demonstrations that the formation of reactive oxygen species (ROS) and the proton motive force (PMF) can both play a role in antibiotic toxicity. The susceptibility of Gram-negative bacteria to aminoglycoside antibiotics, particularly gentamicin, has previously been linked to both the production of ROS and the rate of antibiotic uptake that is mediated by the PMF, although the relative contributions of ROS and PMF to aminoglycoside toxicity has remained poorly understood. Herein, gentamicin was shown to elicit a very modest increase in ROS levels in an aerobically grown Escherichia coli clinical isolate. The well-characterised uncoupler 2,4-dinitrophenol (DNP) was used to disrupt the PMF, which resulted in a significant decrease in gentamicin lethality towards E. coli. DNP did not significantly alter respiratory oxygen consumption, supporting the hypothesis that this uncoupler does not increase ROS production via elevated respiratory oxidase activity. These observations support the hypothesis that maintenance of PMF rather than induction of ROS production underpins the mechanism for how the respiratory chain potentiates the toxicity of aminoglycosides. This was further supported by the demonstration that the uncoupler DNP elicits a dramatic decrease in gentamicin lethality under anaerobic conditions. Together, these data strongly suggest that maintenance of the PMF is the dominant mechanism for the respiratory chain in potentiating the toxic effects of aminoglycosides.

scholarly journals Five decades of research on mitochondrial NADH-quinone oxidoreductase (complex I)

2018 ◽  
Vol 399 (11) ◽  
pp. 1249-1264 ◽  
Author(s):  
Tomoko Ohnishi ◽  
S. Tsuyoshi Ohnishi ◽  
John C. Salerno
Keyword(s):  
Electron Transfer ◽  
Respiratory Chain ◽  
Complex I ◽  
Proton Translocation ◽  
Atp Synthesis ◽  
Mitochondrial Respiratory Chain ◽  
Proton Pumping ◽  
Entry Site ◽  
Quinone Oxidoreductase ◽  
Terminal Electron Acceptor

AbstractNADH-quinone oxidoreductase (complex I) is the largest and most complicated enzyme complex of the mitochondrial respiratory chain. It is the entry site into the respiratory chain for most of the reducing equivalents generated during metabolism, coupling electron transfer from NADH to quinone to proton translocation, which in turn drives ATP synthesis. Dysfunction of complex I is associated with neurodegenerative diseases such as Parkinson’s and Alzheimer’s, and it is proposed to be involved in aging. Complex I has one non-covalently bound FMN, eight to 10 iron-sulfur clusters, and protein-associated quinone molecules as electron transport components. Electron paramagnetic resonance (EPR) has previously been the most informative technique, especially in membranein situanalysis. The structure of complex 1 has now been resolved from a number of species, but the mechanisms by which electron transfer is coupled to transmembrane proton pumping remains unresolved. Ubiquinone-10, the terminal electron acceptor of complex I, is detectable by EPR in its one electron reduced, semiquinone (SQ) state. In the aerobic steady state of respiration the semi-ubiquinone anion has been observed and studied in detail. Two distinct protein-associated fast and slow relaxing, SQ signals have been resolved which were designated SQNfand SQNs. This review covers a five decade personal journey through the field leading to a focus on the unresolved questions of the role of the SQ radicals and their possible part in proton pumping.

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