Energy dependent changes in the cytochromes of the mitochondrial respiratory chain

Wilson, David F.; Brocklehurst, Elizabeth

doi:10.1016/0003-9861(73)90614-0

Cited by 38 publications

(6 citation statements)

References 14 publications

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“…The Soret band is shifted toward the red, and a broad increase ofabsorption is centered near 580 nm (see Fig. 1 (13,16,17). This energy-dependent spectral shift has been attributed to generation of a "high-energy" state of cytochrome a3 that may be directly involved in primary energy conservation (13,18), or more specifically, in proton translocation (1,19,20 Fig.…”

Section: Resultsmentioning

confidence: 99%

Energy-dependent reversal of the cytochrome oxidase reaction.

Wikström¹

1981

Proc. Natl. Acad. Sci. U.S.A.

149

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Energization of isolated rat liver mitochondria with ATP under conditions in which cytochrome c is poised in a highly oxidized state shifts the state of cytochrome oxidase (cytochrome c oxidase; ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) from fully oxidized to two new spectroscopically distinguishable states depending on the applied phosphorylation potential and redox potential at cytochrome c. Both new states are spectrally similar or identical to two previously described intermediates in the reaction between reduced enzyme and O2. The data suggest that the energy-dependent transitions are due to reversed electron transfer from water to ferricytochrome c linked to accumulation of intermediates of O2 reduction at the catalytic heme a3/copper center. Titrations with redox potential indicate that each transition is a one-electron step, a finding that would identify the second observed compound as enzyme-bound peroxide or its equivalent. This is consistent with this compound being spectrally identical to "Compound C," previously described as the reaction product between half-reduced oxidase (two electrons) and O2. On the basis of these data a catalytic scheme of O2 reduction is proposed for the heme a3/copper center of cytochrome oxidase.

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Section: Resultsmentioning

confidence: 99%

Energy-dependent reversal of the cytochrome oxidase reaction.

Wikström¹

1981

Proc. Natl. Acad. Sci. U.S.A.

149

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“…In a series of measurements it was shown that if an Em7.0 of 0.245V was used for cytochrome a, then the same Ek value was found for cytochrome c as for cytochrome a. An E.7.0 value of 0.245V lies within the range 0.210-0.255 V (Lindsay & Wilson & Brocklehurst, 1973) which is found in isolated mitochrondria at various phosphorylation states of the adenine nucleotide system.…”

mentioning

confidence: 81%

Equilibrium relations between the oxidation—reduction reactions and the adenosine triphosphate synthesis in suspensions of isolated liver cells

Wilson

Stubbs

Veech

et al. 1974

Biochemical Journal

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216

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1. The redox state of cytochrome c, cytochrome a and the mitochondrial NAD couple, and the phosphorylation state of the adenine nucleotides, were measured in suspensions of isolated rat liver cells. 2. The DeltaG for the transfer of two electrons from the mitochondrial NAD to the cytochrome c couple is calculated to be 104kJ (24.8kcal). 3. The DeltaG associated with the synthesis of ATP at the measured phosphorylation state is calculated to be 95kJ (22.7kcal)/2mol of ATP. 4. The near equality of DeltaG of the electron-transport process and DeltaG required for ATP synthesis indicates near-equilibrium between the mitochondrial respiratory chain and the extramitochondrial phosphorylation state. 5. The existence of near-equilibrium in the coupled reactions implies that the respiratory activity depends on the ratio [ATP]/[ADP][P(i)] and not on the concentrations of the individual reactants. 6. If the overall system of oxidative phosphorylation is at near-equilibrium, all intermediary reactions must also be at equilibrium. Hence if the intramitochondrial and extramitochondrial phosphorylation states are indeed different, it follows that any differences in the activities of ATP, ADP and P(i) must be coupled to ion gradients and/or potentials across the inner mitochondrial membrane in such a way that translocation occurs without loss of free energy. 7. The metabolic state of the mitochondria in the cell can be defined by the turnover number of the cytochromes, the cytoplasmic phosphorylation state, and the oxidation-reduction potential of the NAD couple, rather than by the availability of ADP, substrate and O(2).

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“…It was found subsequently that there are two types of spectral changes associated with mitochondrial cytochrome oxidase that are directly dependent on the phos phorylation state of the adenine nucleotide system (84,85). One occurs under highly oxidizing conditions in the absence of substrate and in the presence of oxygen and ferricyanide.…”

Section: State Of the Adenine Nucleotide Systemmentioning

confidence: 98%