Resolving the EPR Spectra in the Cytochrome bc (1) Complex from Saccharomyces cerevisiae

MacMillan, Fraser ORCID:, Lange, Christian, Bawn, Matt and Hunte, Carola (2010) Resolving the EPR Spectra in the Cytochrome bc (1) Complex from Saccharomyces cerevisiae. Applied Magnetic Resonance, 37 (1-4). pp. 305-316. ISSN 0937-9347

Full text not available from this repository. (Request a copy)


Quinone molecules are ubiquitous in living organisms. They are found either within the lipid phase of the biological membrane (quinone pool) or are bound in specific binding sites within membrane-bound protein complexes. The biological function of such bound quinones is determined by their ability to be reduced and/or oxidized in two successive one-electron steps. As a result, quinones are involved as one- or two-electron donors or acceptors in a large number of biological electron-transfer steps occurring during respiratory or photosynthetic processes. The intermediate formed by a one-electron reduction step is a semiquinone, which is paramagnetic and can be studied by electron paramagnetic resonance (EPR) spectroscopy. Detailed studies of such states can provide important structural information on these intermediates in such electron-transfer processes. In this study, we focus on the redox-active ubiquinone-6 of the yeast cytochrome bc (1) complex (QCR, ubiquinol: cytochrome c oxidoreductase) from Saccharomyces cerevisiae at the so-called Q(i) site. Although the location of the Q(i) binding pocket is quite well known, details about its exact binding are less clear. Currently, three different X-ray crystallographic studies suggest three different binding geometries for Q(i). Recent studies in the bacterial system (Rhodobacter sphaeroides) have suggested a direct coordination to histidine as proposed in the chicken heart crystal structure model. Using the yeast system we apply EPR and especially relaxation filtered hyperfine (REFINE) spectroscopy to study the Q(i) binding site. N-14-electron spin-echo envelope modulation spectroscopy together with an inversion-recovery filter (REFINE) is applied to resolve the question of whether N-14 modulations arise from interactions to Q (i) (center dot-) or to the Rieske iron-sulphur center. These results are discussed with regard to the location and potential function of Q(i) in the enzyme.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Faculty of Science > Research Groups > Chemistry of Life Processes
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Chemistry of Light and Energy
Depositing User: Rachel Smith
Date Deposited: 18 Jul 2011 14:47
Last Modified: 23 Oct 2022 01:33
DOI: 10.1007/s00723-009-0077-4

Actions (login required)

View Item View Item