Cited by 200Mitochondrial Function and PathologyCoenzyme Q10 studies and effectsRedox biology and oxidative stress

The mechanism of superoxide production by the antimycin-inhibited mitochondrial Q-cycle

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Quinlan, Casey L., Gerencser, Akos A., Treberg, Jason R., Brand, Martin D.·2011·Journal of Biological Chemistry

Abstract

Superoxide production from antimycin-inhibited complex III in isolated mitochondria first increased to a maximum then decreased as substrate supply was modulated in three different ways. In each case, superoxide production had a similar bell-shaped relationship to the reduction state of cytochrome b(566), suggesting that superoxide production peaks at intermediate Q-reduction state because it comes from a semiquinone in the outer quinone-binding site in complex III (Q(o)). Imposition of a membrane potential changed the relationships between superoxide production and b(566) reduction and between b(562) and b(566) redox states, suggesting that b(562) reduction also affects semiquinone concentration and superoxide production. To assess whether this behavior was consistent with the Q-cycle mechanism of complex III, we generated a kinetic model of the antimycin-inhibited Q(o) site. Using published rate constants (determined without antimycin), with unknown rate constants allowed to vary, the model failed to fit the data. However, when we allowed the rate constant for quinol oxidation to decrease 1000-fold and the rate constant for semiquinone oxidation by b(566) to depend on the b(562) redox state, the model fit the energized and de-energized data well. In such fits, quinol oxidation was much slower than literature values and slowed further when b(566) was reduced, and reduction of b(562) stabilized the semiquinone when b(566) was oxidized. Thus, superoxide production at Q(o) depends on the reduction states of b(566) and b(562) and fits the Q-cycle only if particular rate constants are altered when b oxidation is prevented by antimycin. These mechanisms limit superoxide production and short circuiting of the Q-cycle when electron transfer slows.

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  1. Cape, J. L., Bowman, M. K., and Kramer, D. M. (2007) Proc. Natl. Acad. Sci.

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Authors
Quinlan, C. L., Gerencser, A. A., Treberg, J. R., & Brand, M. D.
Affiliations
Buck Institute for Research on Aging (US)
Corresponding author
Quinlan, Casey L.
Venue
Journal of Biological Chemistry
Publisher
Elsevier BV
Published
2011-09
Volume
286
Issue
36
Pages
31361-31372
ISSN
0021-9258 (ISSN-L)
OpenAlex
W2009383015
Cited by
200
References
52
Citations by year
2026: 10 · 2025: 17 · 2024: 11 · 2023: 19 · 2022: 11 · 2021: 21 · 2020: 17 · 2019: 9 · 2018: 11 · 2017: 11 · 2016: 13 · 2015: 10 · 2014: 17 · 2013: 14 · 2012: 9
FWCI
5.20
Type
journal article
Language
en
Open access
Locations
  • Journal of Biological Chemistry (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health
  • National Institute on Aging (R01AG033542, PL1AG032118, P01AG025901)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Mitochondrial Function and Pathology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Coenzyme Q10 studies and effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Redox biology and oxidative stress
Keywords
superoxide production, antimycin, mitochondrial complex III, Q-cycle, cytochrome b562, semiquinone, kinetic modeling, electron transfer, membrane potential, mitochondrial respiration, reactive oxygen species
MeSH terms
Animals, Anti-Bacterial Agents, Antimycin A, Cytochrome b Group, Electron Transport, Female, Kinetics, Mitochondria, Oxidation-Reduction, Quinones, Superoxides, Electron Transport Complex III, Rats, Wistar, Escherichia coli Proteins, Rats

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