The redox states of respiratory-chain components in rat-liver mitochondria I. Effect of varying substrate concentration and of azide

Muraoka, Saburo; Slater, E.C.

doi:10.1016/0005-2728(69)90108-x

Cited by 25 publications

(13 citation statements)

References 20 publications

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“…It is often assumed that there is no net proton pumping and that a near-equilibrium state is reached between the redox and proton translocation reactions. Such a near-equilibrium in State 4 was already concluded by Muraoka and Slater in their seminal work from 1969 35 . Although, in reality, a membrane proton leak balances redox-linked proton translocation by the three respiratory chain complexes, this leak is much slower than the forward and backward reactions of redox-linked proton translocation ensuring that a state near-equilibrium is reached.…”

Section: Discussionsupporting

confidence: 56%

“…Determination of efficiency using Eq. (5) requires knowledge of the force ratio in State 3 (x), which can be calculated from literature data where the redox poise of the NAD + /NADH, ubiquinone/ubiquinol, ferri-/ferrocytochrome c and oxygen/water redox couples have been reported 20 . However, the flux ratio (j) (i.e.…”

Section: Resultsmentioning

confidence: 99%

“…The redox span for the different complexes of the respiratory chain (X 2, or ΔE) may be obtained from the literature as before ( 20 , we have estimated it as follows. We have collected the cases where respiration was studied with succinate and with TMPD + ascorbate as substrates 20 , where there is no or very limited net electron flux across complex I. Instead, the generated ΔP drives electrons backwards from cytochrome c and ubiquinone to NAD + until a steady state is reached, in which the redox reactions of complex I should equilibrate with the ΔP.…”

Section: O H -mentioning

confidence: 99%

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Thermodynamic efficiency, reversibility, and degree of coupling in energy conservation by the mitochondrial respiratory chain

Wikström

Springett

2020

Commun Biol

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The protonmotive mitochondrial respiratory chain, comprising complexes I, III and IV, transduces free energy of the electron transfer reactions to an electrochemical proton gradient across the inner mitochondrial membrane. This gradient is used to drive synthesis of ATP and ion and metabolite transport. The efficiency of energy conversion is of interest from a physiological point of view, since the energy transduction mechanisms differ fundamentally between the three complexes. Here, we have chosen actively phosphorylating mitochondria as the focus of analysis. For all three complexes we find that the thermodynamic efficiency is about 80-90% and that the degree of coupling between the redox and proton translocation reactions is very high during active ATP synthesis. However, when net ATP synthesis stops at a high ATP/ADP. Pi ratio, and mitochondria reach "State 4" with an elevated proton gradient, the degree of coupling drops substantially. The mechanistic cause and the physiological implications of this effect are discussed.

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Section: Discussionsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 99%

Section: O H -mentioning

confidence: 99%

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Thermodynamic efficiency, reversibility, and degree of coupling in energy conservation by the mitochondrial respiratory chain

Wikström

Springett

2020

Commun Biol

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“…1 indicate that TPP + can permeate the mitochondrial membrane about 15-fold faster than DDA § As described above, TPP § does not require a lipid-soluble anion such as TPB-. These facts suggest that TPP + is more surpassing for the membrane potential indicator than DDA § Figure 2A shows the results of simultaneous measurements of TPP +-uptake and of oxygen consumption for the transition between state 3 and state 4, indicating that the change in the TPP + electrode potential Under state-4 condition, the respiratory chain and extra-mitochondrial adenine nucleotide pool are close to thermodynamic equilibrium [30]. Then, the chemiosmotic theory requires that, under state-4 condition, A fiu must also be in near equilibrium with phosphorylation potential, A Gp, which is defined as the free energy change of ATP synthesis.…”

Section: C~ [L-exp[-~pi~7+exp(fa(p/rt)tt]]mentioning

confidence: 93%

Membrane potential of mitochondria measured with an electrode sensitive to tetraphenyl phosphonium and relationship between proton electrochemical potential and phosphorylation potential in steady state

et al. 1979

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The membrane potential of mitochondria was estimated from the accumulation of tetraphenyl phosphonium (TPP+), which was determined with the TPP+-selective electrode developed in the present study. The preparation and some operational parameters of the electrode were described. The kinetics for uptake by mitochondria of TPP+ and DDA+ (dibenzyldimethyl ammonium) were analyzed, and it was found that TPP+ permeated the mitochondrial membrane about 15 times faster than DDA+. The final amounts of accumulation of TPP+ and DDA+ by mitochondria were approximately equal. For the state-4 mitochondria, the membrane potential was about 180 mV (interior negative). Simultaneous measurements of TPP+-uptake and oxygen consumption showed that the transition between states 3 and 4 was detectable by use of the TPP+-electrode. After the TPP+-electrode showed that state-4 was reached, the extra-mitochondrial phosphorylation potential was measured. The difference in pH across the membrane was measured from the distribution of permeant anion, acetate, so as to calculate the proton electrochemical potential. The ratio of extra-mitochondrial phosphorylation potential to proton electro-chemical potential, n was close to 3. This value of n was also found to be 3 when ATP was hydrolyzed under the condition that the respiratory chain was arrested. The implication that n = 3 was discussed.

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“…for active transport processes). Muraoka and Slater (1969) have shown that in resting metabolism the reactions in the respiratory chain approach equilibrium conditions. Thus the net velocities of reactions 1 and 2 would be low in the resting state, and the resulting level of NADH would be determined mainly by the equilibrium constants.…”

Section: Steady-state Conditionsmentioning

confidence: 99%

Fluorometric Studies of Oxidative Metabolism in Isolated Papillary Muscle of the Rabbit

Chapman

1972

The Journal of General Physiology

100

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The fluorometric technique for measuring the levels of reduced pyridine nucleotides was used to study oxidative metabolism in isolated rabbit papillary muscle at 23 0 C. The 100 % standard level of tissue fluorescence was defined as that measured for muscles resting in oxygenated 10 mM pyruvate solution. This level increased 15% with anoxia and decreased 45 % with stimulation in substrate-free solution. Thus, about one-half of the standard tissue fluorescence was metabolically labile and this labile fraction is suggested to be mitochondrial in origin. Decreased tissue fluorescence following mechanical activity was identified with increased oxidation of mitochondrial reduced nicotinamide adenine dinucleotide (NADH) owing to stimulation by adenosine diphosphate (ADP), released during activity, of mitochondrial respiration. The kinetics of the fluorescence transients were slowed fourfold by removal of pyruvate. This effect was not significantly reversed by addition of 10 mM glucose. The time integrals of the fluorescence transients were linearly related to the amounts of mechanical activity in the presence, but not in the absence, of pyruvate. A positive correlation was observed between the steady-state peak tension at constant stimulus rate and the resting level of reduction of pyridine nucleotides in various media. The fluorometric results are interpreted to be indicative of the steady and transient states established by the substrate dehydrogenases and the respiratory chain during oxidative phosphorylation in mitochondria.

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The redox states of respiratory-chain components in rat-liver mitochondria I. Effect of varying substrate concentration and of azide

Cited by 25 publications

References 20 publications

Thermodynamic efficiency, reversibility, and degree of coupling in energy conservation by the mitochondrial respiratory chain

Thermodynamic efficiency, reversibility, and degree of coupling in energy conservation by the mitochondrial respiratory chain

Membrane potential of mitochondria measured with an electrode sensitive to tetraphenyl phosphonium and relationship between proton electrochemical potential and phosphorylation potential in steady state

Fluorometric Studies of Oxidative Metabolism in Isolated Papillary Muscle of the Rabbit

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