Asymmetric and redox-specific binding of quinone and quinol at center N of the dimeric yeast cytochrome bc1 complex : consequences for semiquinone stabilization
- The cytochrome bc1 complex recycles one of the two electrons from quinol (QH2) oxidation at center P by reducing quinone (Q) at center N to semiquinone (SQ), which is bound tightly. We have analyzed the properties of SQ bound at center N of the yeast bc1 complex. The EPR-detectable signal, which reports SQ bound in the vicinity of reduced bH heme, was abolished by the center N inhibitors antimycin, funiculosin, and ilicicolin H, but was unchanged by the center P inhibitors myxothiazol and stigmatellin. After correcting for the EPR-silent SQ bound close to oxidized bH, we calculated a midpoint redox potential (Em) of approximately 90 mV for all bound SQ. Considering the Em values for bH and free Q, this result indicates that center N preferentially stabilizes SQ.bH(3+) complexes. This favors recycling of the electron coming from center P and also implies a >2.5-fold higher affinity for QH2 than for Q at center N, which would potentially inhibit bH oxidation by Q. Using pre-steady-state kinetics, we show that Q does not inhibit the initial rate of bH reduction by QH2 through center N, but does decrease the extent of reduction, indicating that Q binds only when bH is reduced, whereas QH2 binds when bH is oxidized. Kinetic modeling of these results suggests that formation of SQ at one center N in the dimer allows stabilization of SQ in the other monomer by Q reduction after intradimer electron transfer. This model allows maximum SQ.bH(3+) formation without inhibition of Q binding by QH2.
Author: | Raul CovianORCiD, Klaus ZwickerORCiD, Frederik A. Rotsaert, Bernard L. Trumpower |
---|---|
URN: | urn:nbn:de:hebis:30:3-762901 |
DOI: | https://doi.org/https://doi.org/10.1074/jbc.M700662200 |
ISSN: | 0021-9258 |
Parent Title (English): | Journal of biological chemistry |
Publisher: | American Society for Biochemistry and Molecular Biology Publications |
Place of publication: | Bethesda, Md |
Document Type: | Article |
Language: | English |
Date of Publication (online): | 2021/01/04 |
Year of first Publication: | 2007 |
Publishing Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Release Date: | 2024/03/05 |
Volume: | 282.2007 |
Issue: | 33 |
Page Number: | 11 |
First Page: | 24198 |
Last Page: | 24208 |
Institutes: | Biochemie, Chemie und Pharmazie / Biochemie und Chemie |
Dewey Decimal Classification: | 5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie |
Sammlungen: | Universitätspublikationen |
Licence (German): | Creative Commons - CC BY - Namensnennung 4.0 International |