The recognition and redox properties of a component, possibly a quinone, which determines electron transfer rate in ubiquinone‐cytochrome <i>c</i> oxidoreductase of mitochondria

Matsuura, Kiyotaka; Packham, Nigel K.; Müeller, Paul; Dutton, P. Leslie

doi:10.1016/0014-5793(81)80877-0

Cited by 29 publications

(10 citation statements)

References 25 publications

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“…Fig.3A demonstrates that in the presence of myxothiazol, cyt b reduction occurs on a time scale that is independent of that of the redox reactions of cyt cr + CZ. In contrast, in the presence of antimycin, myxothiazol-sensitive cyt b reduction occurs concomitant with the partial reduction of cyt cl + ~2, consistent with expectations concerning the Q,-mediated route to cyt b [8,38].…”

Section: Rcsupporting

confidence: 86%

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

et al. 1984

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Reduction of cytochrome b-560 (analogous to cyt b-562 of mitochondria) via an antimycin-sensitive route has been revealed in chromatophores of the photosynthetic bacterium, Rhodqpseudomonas sphaeroides Ga. Indeed, the results suggest that two reductive mechanisms can be operative. One is consistent with the idea that the quinol generated at the reaction center Q,site enters the Q pool and, via the Q,site, equilibrates with cytochrome b-560. The other reductive mode circumvents redox equilibrium with the pool; we consider that this could result from a direct encounter of the reaction center with the bc, complex perhaps involving a direct Qe-Qc site interaction. This latter reaction is suppressed by occupancy of the Qc site, not only by antimycin but by ubiquinol and ubiquinone.

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Section: Rcsupporting

confidence: 86%

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

et al. 1984

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“…The final aspect of the model to be considered is the rate-limiting step in electron flow through the complex and thus the point stimulated in the respiratory chain of liver mitochondria after glucagon treatment of the rat. Elegant experiments have been performed recently with a hybrid electrontransport system comprising the photochemical reaction centre of Rhodopseudomonas sphaeroides and purified Complex III (Matsuura et al, 1981). Single-flash kinetics indicate that the rate-limiting step in electron flow between cytochrome b562 and cytochrome c/cl involves a ubiquinoneubiquinol interconversion.…”

Section: Discussionmentioning

confidence: 99%

The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain. Evidence from inhibition studies for a modified ‘Q cycle’

Halestrap¹

1982

Biochemical Journal

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1. Cytochrome spectra of the liver and heart mitochondria incubated under various conditions are presented to compare the effects of antimycin, colletotrichin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) additions. 2. Under aerobic conditions, in State 4, in the presence of uncoupler or in the presence of cyanide, all three inhibitors caused oxidation of cytochromes c and c1, but different changes in the spectra of the b cytochromes. Antimycin caused oxidation of a peak at 558 nm and reduction of peaks at 562 nm and 566 nm, whereas colletotrichin caused reduction of peaks at 558 nm and 566 nm and oxidation at 562 nm. HQNO had an effect on the spectra intermediate between those of the two other inhibitors. 3. Under aerobic conditions in the presence of 5 mM-succinate and 5 mM-fumarate, antimycin caused reduction of a peak at 566 nm and oxidation of a peak at 558 nm, whereas colletotrichin had the reverse effect and HQNO caused reduction of a peak at 562 nm. 4. Colletotrichin inhibition of the ADP-stimulated oxidation of glutamate + malate was enhanced by succinate addition and declined again with rotenone addition. Similar but smaller effects were seen with inhibition by antimycin and HQNO. 5. Cytochrome spectra are shown of the effects of ADP and uncoupler addition to stimulate respiration progressively. 6. The results are interpreted in terms of a modified 'Q cycle' [Mitchell (1976) J. Theor. Biol. 62, 327-367] in which the three inhibitors are postulated to displace ubiquinone and ubisemiquinone specifically bound to cytochromes b on both sides of the membrane. 7. It is suggested that cytochromes b558 and b566 are the same b cytochrome located on the outer surface of the membrane, but binding ubisemiquinone or colletotrichin and ubiquinone or antimycin respectively. Cytochrome b562 is postulated to be on the inner surface of the mitochondrial membrane and to bind either ubiquinone or ubisemiquinone, HQNO would bind to the reduced form of the cytochrome and colletotrichin to the oxidized form. 8. Sites for the locus of action of glucagon and the protonmotive force on electron flow are suggested.

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“…interactions with the Q o site inhabitants (31). Thus, any change in the hydrogen-bonding interactions between the [2Fe2S] red and UQ or UQH 2 might also affect the E m of this EPR transition.…”

Section: Additional Components Other Than Hydrogen Bonding Of [2fe2s]mentioning

confidence: 95%

“…It is known that class II Q o site inhibitors such as stigmatellin (26) or UHDBT (27,28) considerably increase the E m of the [2Fe2S] cluster of the Fe-S subunit of the cyt bc 1 by stabilizing its reduced form, while class I Q o site inhibitors such as myxothiazol or MOA-stilbene decrease it slightly (20,29,30). Moreover, the EPR g x transition of the [2Fe2S] cluster of the Fe-S protein responds to the Q pool redox state, with the g x ) 1.8 signal titrating with an E m7 of approximately 90 mV (31). The g x transition changes from a narrow g ) 1.80 trough when the Q pool is oxidized to a broader g ) 1.77 trough when the Q pool is reduced, and to a very broad g ) 1.76 signal when Q/QH 2 depleted membranes were used.…”

Section: The Increase In the E M7 Of The +2ala Strain [2fe2s]mentioning

confidence: 99%

The Raised Midpoint Potential of the [2Fe2S] Cluster of Cytochromebc₁Is Mediated by Both the Q_oSite Occupants and the Head Domain Position of the Fe−S Protein Subunit

et al. 2004

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We have previously reported that mutant strains of Rhodobacter capsulatus that have alanine insertions (+nAla mutants) in the hinge region of the iron sulfur (Fe-S) containing subunit of the bc(1) complex have increased redox midpoint potentials (E(m)) for their [2Fe2S] clusters. The alteration of the E(m) in these strains, which contain mutations far from the metal binding site, implied that the local environment of the metal center is indirectly altered by a change in the interaction of this subunit with the hydroquinone oxidizing (Q(o)) site [Darrouzet, E., Valkova-Valchanova, M., and Daldal, F. (2002) J. Biol. Chem. 277, 3464-3470]. Subsequently, the E(m) changes have been proposed to be predominantly due to a stronger or more stabilized hydrogen bonding between the reduced [2Fe2S] cluster and the Q(o) site inhabitant ubiquinone (Q) [Shinkarev, V. P., Kolling, D. R. J., Miller, T. J., and Crofts, A. R. (2002) Biochemistry 41, 14372-14382]. To further investigate this issue, Fe-S protein-Q interactions were monitored by electron paramagnetic resonance (EPR) spectroscopy and the findings indicated that the wild type and mutant proteins interactions with Q are similar. Moreover, when the Q(pool) was chemically depleted, the E(m) of the [2Fe2S] cluster in mutant bc(1) complexes remained more positive than a similarly treated native enzyme (e.g., the [2Fe2S] E(m) of the +2Ala mutant was 55 mV more positive than the wild type). These data suggest that the increased E(m) of the [2Fe2S] cluster in the +nAla mutants is in part due to the cluster's interaction with Q, and in part to additional factors that are independent of hydrogen bonding to Q. One such factor, the possibility of a different position of the Fe-S at the Q(o) site of the mutant proteins versus the native enzyme, was addressed by determining the orientation of the [2Fe2S] cluster in the membrane using EPR spectroscopy. In the case of the +2Ala mutant, the [2Fe2S] cluster orientation in the absence of inhibitor is different than that seen in the native enzyme. However, the +2Ala mutant cluster shared a similar orientation with the native enzyme when both samples were exposed to either stigmatellin or myxothiazol. In addition, Q(pool) extracted membranes of +2Ala mutant exhibited fewer overall orientations, with the predominant one being more similar to that observed in the non-Q-depleted membranes of the +2Ala mutant than the Q-depleted membranes of a wild-type strain. Therefore, additional component(s) that are independent of Q(o) site inhabitants and that originate from the newly observed orientations of the [2Fe2S] clusters in the +nAla mutants also contribute to the increased midpoint potentials of their [2Fe2S] clusters. While the molecular basis of these components remains to be determined, salient implications of these findings in terms of Q(o) site catalysis are discussed.

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The recognition and redox properties of a component, possibly a quinone, which determines electron transfer rate in ubiquinone‐cytochrome c oxidoreductase of mitochondria

Cited by 29 publications

References 25 publications

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain. Evidence from inhibition studies for a modified ‘Q cycle’

The Raised Midpoint Potential of the [2Fe2S] Cluster of Cytochromebc₁Is Mediated by Both the Q_oSite Occupants and the Head Domain Position of the Fe−S Protein Subunit

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The recognition and redox properties of a component, possibly a quinone, which determines electron transfer rate in ubiquinone‐cytochrome c oxidoreductase of mitochondria

Cited by 29 publications

References 25 publications

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc1 complex

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc1 complex

The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain. Evidence from inhibition studies for a modified ‘Q cycle’

The Raised Midpoint Potential of the [2Fe2S] Cluster of Cytochromebc1Is Mediated by Both the QoSite Occupants and the Head Domain Position of the Fe−S Protein Subunit

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Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

Two distinct quinone‐modulated modes of antimycin‐sensitive cytochrome b reduction in the cytochrome bc₁ complex

The Raised Midpoint Potential of the [2Fe2S] Cluster of Cytochromebc₁Is Mediated by Both the Q_oSite Occupants and the Head Domain Position of the Fe−S Protein Subunit