The redox states of respiratory-chain components in rat-liver mitochondria II. The “crossover” on the transition from State 3 to State 4

Muraoka, Saburo; Slater, E.C.

doi:10.1016/0005-2728(69)90109-1

Cited by 44 publications

(18 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In such conditions ΔE h is shifted to approximately 364 mV during respiration on β-hydroxybutyrate (calculated from data in ref. 19), in which case the maximum value of n is 2.14, and a maximum H þ ∕2 e − ratio of 4 is possible. For this reason it will be important to obtain an independent measure of the H þ ∕2 e − ratio under conditions of active ATP synthesis [i.e., in state 3 mitochondria (see below)].…”

Section: Resultsmentioning

confidence: 99%

Stoichiometry of proton translocation by respiratory complex I and its mechanistic implications

Wikström

Hummer

2012

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

101

View full text Add to dashboard Cite

Complex I (NADH-ubiquinone oxidoreductase) in the respiratory chain of mitochondria and several bacteria functions as a redoxdriven proton pump that contributes to the generation of the protonmotive force across the inner mitochondrial or bacterial membrane and thus to the aerobic synthesis of ATP. The stoichiometry of proton translocation is thought to be 4 H þ per NADH oxidized (2 e − ). Here we show that a H þ ∕2 e − ratio of 3 appears more likely on the basis of the recently determined H þ ∕ATP ratio of the mitochondrial F 1 F o -ATP synthase of animal mitochondria and of a set of carefully determined ATP∕2 e − ratios for different segments of the mitochondrial respiratory chain. This lower H þ ∕2 e − ratio of 3 is independently supported by thermodynamic analyses of experiments with both mitochondria and submitochondrial particles. A reduced H þ ∕2 e − stoichiometry of 3 has important mechanistic implications for this proton pump. In a rough mechanistic model, we suggest a concerted proton translocation mechanism in the three homologous and tightly packed antiporterlike subunits L, M, and N of the proton-translocating membrane domain of complex I.cell respiration | proton pumping | conformational changes | phosphorylation potential C omplex I is the entry point of the respiratory chain in mitochondria and many bacteria and structurally by far the most complicated of the three respiratory chain complexes with protonmotive activity, viz. I, III, and IV. Complex I is an L-shaped integral membrane protein. Its hydrophilic arm, which protrudes out of the membrane on the negatively charged N side, contains the NADH-oxidizing FMN site, a set of iron sulfur centers, and a binding site for ubiquinone (1-3). The membrane domain includes seven subunits that in mitochondria are all encoded by mtDNA and that are present also in bacteria (see Fig. 1). Three of these subunits*, L, M, and N, are homologous to one another as well as to certain bacterial proton/cation antiporters (2, 3, 6). They share structural features, such as two disrupted transmembrane α-helices (4) and conserved lysines within the membrane domain, which appear to be important in the proton-pumping mechanism (7-9).When considering possible mechanisms of redox-linked proton translocation by complex I, some kind of conformational coupling has appeared obvious due to the long distance between the redoxactive cofactors in the hydrophilic domain and the likely protontranslocating subunits in the membrane domain. The crystal structures (4, 10) revealed a most uncommon long amphipathic α-helix that is part of the distal subunit L. It passes along almost the entire N surface of the membrane domain and is followed by a transmembrane helix on the proximal side of subunit N, thus "wrapping up" the three antiporter-like subunits. This helix has been suggested to communicate redox-dependent conformational changes in the hydrophilic domain to the membrane subunits (4, 10).Here we first reexamine the stoichiometry of redox-coupled proton translocation in complex I and...

show abstract

Section: Resultsmentioning

confidence: 99%

Stoichiometry of proton translocation by respiratory complex I and its mechanistic implications

Wikström

Hummer

2012

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

101

View full text Add to dashboard Cite

show abstract

“…The revaluation of the proton pumping stoichiometry from 4 to 3 (8) is partly based on the report by Hinkle et al (7) that the redox span of complex I in state-4 is 360 mV and the report by Nicholls (26) that the proton motive force generated in state-4 is 220 mV giving a stoichiometry of 3.3H ϩ /2e Ϫ . However, Hinkle et al, (7) used data from Muraoka and Slater (27) who reported that the measurements were carried out in a buffer containing 10 mM of inorganic phosphate. Nicholls (26) reports that ⌬P is actually 178mV under these conditions (Fig.…”

Section: Discussionmentioning

confidence: 99%

Mammalian Complex I Pumps 4 Protons per 2 Electrons at High and Physiological Proton Motive Force in Living Cells*

Ripple

Kim

Springett

2013

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Thus, in cases where the change in E m of cytochrome a is larger than the change in redox potential (Eh) of cytochrome c + cl (and a) a cross-over point is observed between these redox carriers. However, when the shift in E h is larger than the shift in E m, both cytochromes c + cl and a become more oxidized in state 4 to state 3 transition (the cross-over is then 'beyond' cytochrome a, see [33] ). Thus the cross-over point identifies an energy-controlled step of electron transfer in the respiratory chain (not necessarily a step of energy conservation, [34] and section 5.1.…”

Section: The Cross-over Point Between Cytochromesmentioning

confidence: 99%

A re‐evaluation of the spectral, potentiometric and energy‐linked properties of cytochrome c oxidase in mitochondria

et al. 1976

View full text Add to dashboard Cite

The redox states of respiratory-chain components in rat-liver mitochondria II. The “crossover” on the transition from State 3 to State 4

Cited by 44 publications

References 9 publications

Stoichiometry of proton translocation by respiratory complex I and its mechanistic implications

Stoichiometry of proton translocation by respiratory complex I and its mechanistic implications

Mammalian Complex I Pumps 4 Protons per 2 Electrons at High and Physiological Proton Motive Force in Living Cells*

A re‐evaluation of the spectral, potentiometric and energy‐linked properties of cytochrome c oxidase in mitochondria

Contact Info

Product

Resources

About