Proton translocation coupled to ubiquinol oxidation in Paracoccus denitrificans

1979 ◽  
Vol 57 (2) ◽  
pp. 172-177 ◽  
Author(s):  
Hugh G. Lawford
Keyword(s):  
Respiratory Chain ◽  
Oxidase Activity ◽  
Paracoccus Denitrificans ◽  
Electron Flow ◽  
Proton Translocation ◽  
Energy Coupling ◽  
Ubiquinol Oxidase ◽  
Transport Chain ◽  
Flow Through ◽  
Chemiosmotic Coupling

Measurements were made of the stoichiometry of proton translocation associated with electron flow through the cytochrome-dependent region of the aerobically induced respiratory chain of Paracoccus denitrificans using the pulse oxidant method and rotenone to inhibit NADH dehydrogenase activity. Paracoccus denitrificans (ATCC 13543) was grown aerobically in carbon-limited continuous culture D = 0.27 h−1D, dilution rate per hour) with succinate as sole carbon and energy source. Oxidation of exogenous ubiquinol1 by starved cells was significantly accelerated by treatment of the cells with lysozyme. Spectrophotometric assay of ubiquinol1 oxidase activity in rotenone-poisoned spheroplasts revealed an apparent Km of 25 μM and a Vmax of 217 nmol/min per milligram protein. In site 1 poisoned spheroplasts proton translocation was dependent on the presence of added respiratory substrate, either succinate or ubiquinol1, where the observed ratios of protons ejected from the membrane per atom of oxygen consumed (← H+: O) were 5.3 and 5.2 respectively. The rate of proton translocation associated with succinate and ubiquinol1 oxidation was significantly decreased in the presence of antimycin A and completely abolished with cyanide. Net proton translocation was not observed after the addition of uncoupler (CCCP). Assuming there are two potential sites of energy conservation associated with the region of the respiratory chain from ubiquinone to cytochrome oxidase (i.e., ubiquinol oxidase activity), then the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling or conservation site (← H+: site) ratio in P. denitrificans is closer to 3 than 2 as predicted by Mitchell's chemiosmotic coupling hypothesis.

scholarly journals Involvement of the cbb3-Type Terminal Oxidase in Growth Competition of Bacteria, Biofilm Formation, and in Switching between Denitrification and Aerobic Respiration

2020 ◽  
Vol 8 (8) ◽  
pp. 1230
Author(s):  
Igor Kučera ◽  
Vojtěch Sedláček
Keyword(s):  
Paracoccus Denitrificans ◽  
Aerobic Denitrification ◽  
Wild Type ◽  
Bacterial Strains ◽  
Aerobic Growth ◽  
Limited Growth ◽  
Terminal Oxidases ◽  
Ubiquinol Oxidase ◽  
Fitness Advantage ◽  
Transport Chain

Paracoccus denitrificans has a branched electron transport chain with three terminal oxidases transferring electrons to molecular oxygen, namely aa3-type and cbb3-type cytochrome c oxidases and ba3-type ubiquinol oxidase. In the present study, we focused on strains expressing only one of these enzymes. The competition experiments showed that possession of cbb3-type oxidase confers significant fitness advantage during oxygen-limited growth and supports the biofilm lifestyle. The aa3-type oxidase was shown to allow rapid aerobic growth at a high oxygen supply. Activity of the denitrification pathway that had been expressed in cells grown anaerobically with nitrate was fully inhibitable by oxygen only in wild-type and cbb3 strains, while in strains aa3 and ba3 dinitrogen production from nitrate and oxygen consumption occurred simultaneously. Together, the results highlight the importance of the cbb3-type oxidase for the denitrification phenotype and suggest a way of obtaining novel bacterial strains capable of aerobic denitrification.

scholarly journals In vitro evidence that phytanic acid compromises Na+,K+-ATPase activity and the electron flow through the respiratory chain in brain cortex from young rats

2010 ◽  
Vol 1352 ◽  
pp. 231-238 ◽  
Author(s):  
Estela Natacha Brandt Busanello ◽  
Carolina Maso Viegas ◽  
Alana Pimentel Moura ◽  
Anelise Miotti Tonin ◽  
Mateus Grings ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Respiratory Chain ◽  
Phytanic Acid ◽  
Brain Cortex ◽  
Electron Flow ◽  
Young Rats ◽  
Flow Through

On the Role of Plastoquinone in Photosynthesis

1971 ◽  
Vol 26 (4) ◽  
pp. 341-352 ◽  
Author(s):  
H. Böhme ◽  
S. Reimer ◽  
A. Trebst
Keyword(s):  
Photosystem Ii ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cyclic System ◽  
Transport Chain ◽  
Cyclic Photophosphorylation ◽  
Intact Chloroplasts ◽  
Flow Through

Dibromothymoquinone and its hydroquinone are inhibitors of non cyclic electron flow from water to NADP, anthraquinone or methylviologen. The inhibition is competetively reversed by plastoquinone. It appears that dibromothymoquinone is an antagonist of plastoquinone and that it prevents the enzymic (by the next endogenous carrier of the chloroplast electron transport chain) but not the chemical (by ferricyanide) reoxidation of reduced plastoquinone. This follows from the result that the photoreduction of ferricyanide and DCPIP * is not inhibited by dibromothymoquinone in sonicated chloroplasts and is inhibited in intact chloroplasts to only 60% or 80% respectively. It is concluded that dibromothymoquinone does not inhibit photoreductions by photosystem II.According to their response to dibromothymoquinone, cyclic photophosphorylations can be subdivided in those requiring plastoquinone and those which do not. Menadione catalyzed cyclic photophosphorylation is inhibited by dibromothymoquinone, whereas the PMS catalyzed system is not. The DAD cyclic system is only partly inhibited by dibromothymoquinone. The PMS catalyzed cyclic photophosphorylation in the presence of dibromothymoquinone is antimycin sensitive, which suggests that the PMS system can switch from a plastoquinone dependent system to a plastoquinone independent, but cytochrome b dependent system, which is now antimycin sensitive. Ferredoxin catalyzed cyclic photophosphorylation is inhibited by dibromothymoquinone as well as by antimycin. The data indicate that non cyclic electron flow through both photosystems is obligatory dependent on plastoquinone, whereas cyclic systems do not necessarily include plastoquinone. The relevance of the results to the possibility of different coupling sites in cyclic and non cyclic electron flow systems is discussed.

scholarly journals ROS signalling requires uninterrupted electron flow and is lost during ageing in flies

2021 ◽  
Author(s):  
Charlotte Graham ◽  
Rhoda Stefanatos ◽  
Angeline E.H. Yek ◽  
Ruth V. Spriggs ◽  
Samantha H.Y. Loh ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Flux ◽  
Electron Flow ◽  
Oxygen Species ◽  
Transport Chain ◽  
Response To Stress ◽  
Respiratory Complex I ◽  
Flow Through ◽  
Ros Signalling ◽  
Reverse Electron Transport

Mitochondrial Reactive Oxygen Species (mtROS) are cellular messengers essential for cellular homeostasis. In response to stress, reverse electron transport (RET) by respiratory complex I generates high levels of mtROS. Suppression of ROS produced via RET (ROS-RET) reduces survival under stress, while activation of ROS-RET extends lifespan in basal conditions. Here, we demonstrate that ROS-RET signalling requires increased electron entry and uninterrupted electron flow through the electron transport chain (ETC). We found that ROS-RET is abolished in old fruit flies where electron flux is reduced. Instead, mitochondria in aged flies produce consistently high levels of mtROS. Finally, we demonstrate that in young flies reduction of electron exit from the ETC, but not electron entry, phenocopies mtROS generation observed in old individuals. Our results define the mechanism by which ROS signalling is lost during ageing.

Energy transduction in the mitochondrionlike bacterium Paracoccus denitrificans during carbon- or sulphate-limited aerobic growth in continuous culture

1978 ◽  
Vol 56 (1) ◽  
pp. 13-22 ◽  
Author(s):  
H. G. Lawford
Keyword(s):  
Growth Rate ◽  
Electron Transport ◽  
Continuous Culture ◽  
Respiratory Chain ◽  
Paracoccus Denitrificans ◽  
Proton Translocation ◽  
Short Interval ◽  
Specific Inhibitor ◽  
Growth Yield ◽  
Aerobic Growth

Paracoccus denitrificans was grown in carbon-limited aerobic continuous culture (critical dilution rate (Dc) = 0.48 h−1). The molar growth yield for carbon (succinate or malate) was constant at about 60 over a broad dilution range (growth rate) from 0.10 to 0.48 h−1. Measurements of the stoichiometry of proton translocation associated with the oxidation of endogenous substrates yielded a ratio of protons ejected from the cell per atom of oxygen consumed (→H+:O) of 8.55 which decreased to 5.85 in the presence of piericidin A (PA), a specific inhibitor of NADH dehydrogenase (EC 1.6.99.3). With starved cells, the observed →H+:O associated with the oxidation of added succinate in the presence of PA was 5.61. These observed →H+:O's represent an underestimation since no correction was made for proton backflow during the short interval of respiratory activity. Aerobic growth of Pc. denitrificans in the chemostat becomes sulphate limited at entering concentrations of sulphate <300 μM. Neither the maximum specific growth rate (measured at Dc) nor the observed molar growth yield for succinate decreased under sulphate limitation. The NADH oxidase in electron transport particles prepared from sulphate-limited cells was completely inhibited by PA. The stoichiometry of proton translocation associated with malate oxidation was similarly unaffected by sulphate limitation. It is concluded that (a) the respiratory chain of aerobic, heterotrophically grown Pc. denitrificans possesses three sites of energy conservation, including site III, (b) the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling site is 3, and (c) that sulphate limitation does not lead to a loss of proton translocation associated with the cytochrome-independent region of the respiratory chain.

scholarly journals Inhibition of electron flow through complex I of the mitochondrial respiratory chain of Ehrlich ascites carcinoma cells by methylglyoxal

1994 ◽  
Vol 303 (1) ◽  
pp. 69-72 ◽  
Author(s):  
S Ray ◽  
S Dutta ◽  
J Halder ◽  
M Ray
Keyword(s):  
Oxygen Consumption ◽  
Respiratory Chain ◽  
Complex I ◽  
Electron Flow ◽  
Mitochondrial Respiratory Chain ◽  
Ehrlich Ascites Carcinoma ◽  
Inhibitory Effect ◽  
Ehrlich Ascites ◽  
Flow Through ◽  
Mitochondrial Respiratory

The effect of methylglyoxal on the oxygen consumption of Ehrlich-ascites-carcinoma (EAC)-cell mitochondria was tested by using different respiratory substrates, electron donors at different segments of the mitochondrial respiratory chain and site-specific inhibitors to identify the specific respiratory complex which might be involved in the inhibitory effect of methylglyoxal on the oxygen consumption by these cells. The results indicate that methylglyoxal strongly inhibits ADP-stimulated alpha-oxo-glutarate and malate plus pyruvate-dependent respiration, whereas, at a much higher concentration, methylglyoxal fails to inhibit succinate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinol, an artificial electron donor. Moreover, methylglyoxal cannot inhibit oxygen consumption when the NNN'N′-tetramethyl-p-phenylenediamine by-pass is used. The inhibitory effect of methylglyoxal is identical on both ADP-stimulated and uncoupler-stimulated respiration. Lactaldehyde, a catabolite of methylglyoxal, can exert a protective effect on the inhibition of EAC-cell mitochondrial respiration by methylglyoxal. We suggest that methylglyoxal possibly inhibits the electron flow through complex I of the EAC-cell mitochondrial respiratory chain.

Mitochondrial function in flying honeybees (Apis mellifera): respiratory chain enzymes and electron flow from complex III to oxygen

2000 ◽  
Vol 203 (5) ◽  
pp. 905-911 ◽  
Author(s):  
R.K. Suarez ◽  
J.F. Staples ◽  
J.R. Lighton ◽  
O. Mathieu-Costello
Keyword(s):  
Surface Area ◽  
Muscle Mass ◽  
Respiratory Chain ◽  
Mitochondrial Function ◽  
Electron Flow ◽  
Complex Iii ◽  
High Mass ◽  
Metabolic Rates ◽  
Turnover Rates ◽  
Respiratory Enzymes

The biochemical bases for the high mass-specific metabolic rates of flying insects remain poorly understood. To gain insights into mitochondrial function during flight, metabolic rates of individual flying honeybees were measured using respirometry, and their thoracic muscles were fixed for electron microscopy. Mitochondrial volume densities and cristae surface densities, combined with biochemical data concerning cytochrome content per unit mass, were used to estimate respiratory chain enzyme densities per unit cristae surface area. Despite the high content of respiratory enzymes per unit muscle mass, these are accommodated by abundant mitochondria and high cristae surface densities such that enzyme densities per unit cristae surface area are similar to those found in mammalian muscle and liver. These results support the idea that a unit area of mitochondrial inner membrane constitutes an invariant structural unit. Rates of O(2) consumption per unit cristae surface area are much higher than those estimated in mammals as a consequence of higher enzyme turnover rates (electron transfer rates per enzyme molecule) during flight. Cytochrome c oxidase, in particular, operates close to its maximum catalytic capacity (k(cat)). Thus, high flux rates are achieved via (i) high respiratory enzyme content per unit muscle mass and (ii) the operation of these enzymes at high fractional velocities.

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