The Dimeric Structure of the Cytochrome Bc(1) Complex Prevents Center P Inhibition by Reverse Reactions at Center N
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Biophysics
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Energy transduction in the cytochrome bc(1) complex is achieved by catalyzing opposite oxido-reduction reactions at two different quinone binding sites. We have determined the pre-steady state kinetics of cytochrome b and c(1) reduction at varying quinol/quinone ratios in the isolated yeast bc(1) complex to investigate the mechanisms that minimize inhibition of quinol oxidation at center P by reduction of the b(H) heme through center N. The faster rate of initial cytochrome b reduction as well as its lower sensitivity to quinone concentrations with respect to cytochrome c(1) reduction indicated that the b(H) hemes equilibrated with the quinone pool through center N before significant catalysis at center P occurred. The extent of this initial cytochrome b reduction corresponded to a level of b(H) heme reduction of 33%-55% depending on the quinol/quinone ratio. The extent of initial cytochrome c(1) reduction remained constant as long as the fast electron equilibration through center N reduced no more than 50% of the b(H) hemes. Using kinetic modeling, the resilience of center P catalysis to inhibition caused by partial pre-reduction of the b(H) hemes was explained using kinetics in terms of the dimeric structure of the bc(1) complex which allows electrons to equilibrate between monomers.
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Moe A, Dimogkioka A, Rapaport D, Ojemyr L, Brzezinski P Proc Natl Acad Sci U S A. 2023; 120(46):e2307697120.
PMID: 37939086 PMC: 10655221. DOI: 10.1073/pnas.2307697120.
Moe A, Di Trani J, Rubinstein J, Brzezinski P Proc Natl Acad Sci U S A. 2021; 118(11).
PMID: 33836592 PMC: 7980474. DOI: 10.1073/pnas.2021157118.
Sarewicz M, Pintscher S, Pietras R, Borek A, Bujnowicz L, Hanke G Chem Rev. 2021; 121(4):2020-2108.
PMID: 33464892 PMC: 7908018. DOI: 10.1021/acs.chemrev.0c00712.
Hoang N, Strogolova V, Mosley J, Stuart R, Hosler J J Biol Chem. 2019; 294(46):17669-17677.
PMID: 31591265 PMC: 6873203. DOI: 10.1074/jbc.RA119.010317.
Markevich N, Hoek J Biochim Biophys Acta. 2015; 1847(6-7):656-79.
PMID: 25868872 PMC: 4426091. DOI: 10.1016/j.bbabio.2015.04.005.