The cytochrome bc1 complex is an energy-transducing enzyme that participates in cell respiration in oxygen utilizing eukaryotic cells and is located in the inner mitochondrial membrane. A similar bc1 complex is located in the plasma membrane of many bacteria, where it takes part in respiration, denitrification, nitrogen fixation, and cyclic photosynthetic electron transfer, depending on the species. In all of these organisms the bc1 complex oxidizes a membrane-localized quinol and reduces a water-soluble, c-type cytochrome and links this electron transfer reaction to translocation of protons across the membrane in which the bc1 complex resides. The bc1 complexes from mitochondria of several species have been crystallized and the mechanism of the enzyme, the protonmotive Q cycle, is partly understood. The long term objectives of this research are to understand the mechanism of the cytochrome bc1 complex and to elucidate the pathway by which the subunits of this oligomeric enzyme complex are assembled into the inner mitochondrial membrane.
The specific aims of the current research project are to answer the following questions regarding the mechanism. - Is ubiquinol oxidation a concerted or sequential reaction? - What is the structural basis of negative cooperativity in the binding of ubiquinol? - How are protons conducted to and from the ubiquinone and ubiquinol reaction sites? - How does ubisemiquinone stability affect the rate of ubiquinone reduction? We plan to investigate these questions in the cytochrome bc1 complex of the yeast Saccharomyces cerevisiae, since this enzyme can be modified by molecular genetics methods and isolated in quantities sufficient for biochemical and biophysical characterization.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM020379-35
Application #
7333238
Study Section
Physical Biochemistry Study Section (PB)
Program Officer
Anderson, Vernon
Project Start
1976-06-01
Project End
2010-11-30
Budget Start
2007-12-01
Budget End
2010-11-30
Support Year
35
Fiscal Year
2008
Total Cost
$574,006
Indirect Cost
Name
Dartmouth College
Department
Biochemistry
Type
Schools of Medicine
DUNS #
041027822
City
Hanover
State
NH
Country
United States
Zip Code
03755
Hughes, Louise M; Lanteri, Charlotte A; O'Neil, Michael T et al. (2011) Design of anti-parasitic and anti-fungal hydroxy-naphthoquinones that are less susceptible to drug resistance. Mol Biochem Parasitol 177:12-9
Hughes, Louise M; Covian, Raul; Gribble, Gordon W et al. (2010) Probing binding determinants in center P of the cytochrome bc(1) complex using novel hydroxy-naphthoquinones. Biochim Biophys Acta 1797:38-43
Castellani, Michela; Covian, Raul; Kleinschroth, Thomas et al. (2010) Direct demonstration of half-of-the-sites reactivity in the dimeric cytochrome bc1 complex: enzyme with one inactive monomer is fully active but unable to activate the second ubiquinol oxidation site in response to ligand binding at the ubiquinone reducti J Biol Chem 285:502-10
Covian, Raul; Trumpower, Bernard L (2009) The rate-limiting step in the cytochrome bc1 complex (Ubiquinol-Cytochrome c Oxidoreductase) is not changed by inhibition of cytochrome b-dependent deprotonation: implications for the mechanism of ubiquinol oxidation at center P of the bc1 complex. J Biol Chem 284:14359-67
Rottenberg, Hagai; Covian, Raul; Trumpower, Bernard L (2009) Membrane potential greatly enhances superoxide generation by the cytochrome bc1 complex reconstituted into phospholipid vesicles. J Biol Chem 284:19203-10
Ding, Martina G; di Rago, Jean-Paul; Trumpower, Bernard L (2009) Combining Inhibitor Resistance-conferring Mutations in Cytochrome b Creates Conditional Synthetic Lethality in Saccharomyces cerevisiae. J Biol Chem 284:8478-85
Zara, Vincenzo; Conte, Laura; Trumpower, Bernard L (2009) Evidence that the assembly of the yeast cytochrome bc1 complex involves the formation of a large core structure in the inner mitochondrial membrane. FEBS J 276:1900-14
Covian, Raul; Trumpower, Bernard L (2009) Ilicicolin Inhibition and Binding at Center N of the Dimeric Cytochrome bc1 Complex Reveal Electron Transfer and Regulatory Interactions between Monomers. J Biol Chem 284:8614-20
Covian, Raul; Trumpower, Bernard L (2008) The dimeric structure of the cytochrome bc(1) complex prevents center P inhibition by reverse reactions at center N. Biochim Biophys Acta 1777:1044-52
Rotsaert, Frederik A J; Ding, Martina G; Trumpower, Bernard L (2008) Differential efficacy of inhibition of mitochondrial and bacterial cytochrome bc1 complexes by center N inhibitors antimycin, ilicicolin H and funiculosin. Biochim Biophys Acta 1777:211-9

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