Our objective is to continue elucidation of the molecular reaction mechanisms of the ubiquinone (Q)-mediated mitochondrial electron transfer and energy conservation through study of the two Q-binding protein systems, QPs and QPc, in succinate-Q and ubiquinol-cytochrome c reductase, respectively. The involvement of specific Q-binding proteins (sites) in the mitochondrial electron transfer system has been established and isolated or identified during past support periods. The next step will be the isolation and characterization of active Q-binding proteins, and elucidation of the structure of the Q-binding sites. Multiple approaches will be taken to study the Q-binding sites and Q:protein interaction in both ubiquinol-cytochrome c reductase and succinate-Q reductase. These include: (1) isolation and sequencing of the Q-binding peptides from the isolated Q-binding proteins, (2) organic synthesis of Q derivatives with different functional (electron donating or accepting) properties, and Q derivatives with detectable groups for studying the Q:protein interaction, (3) chemical modification of the Q-binding site, and (4) immunological characterization of the Q-binding sites and proton translocation sites (domains) of Q-binding proteins. The interaction between succinate-Q reductase and ubiquinol cytochrome reductase will be studied by chemical and photoaffinity double labeling technique and by differential scanning calorimetry. The possible involvement of free Q in electron transfer and proton translocation will also be examined. The acceptance of the principle of the chemiosmotic energy coupling hypothesis has given Q a central role in bioenergetics. Success in the proposed research will increase our knowledge of electron transfer and proton translocation reactions. In addition, elucidation of the Q-binding site and Q:protein interaction will provide information crucial to understanding the mechanism of the generation of superoxide, and thus be useful in future investigations of cytotoxicity and aging.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Physical Biochemistry Study Section (PB)
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Oklahoma State University Stillwater
Schools of Earth Sciences/Natur
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Su, Ting; Wang, Qiyu; Yu, Linda et al. (2015) Universal Stress Protein Regulates Electron Transfer and Superoxide Generation Activities of the Cytochrome bc1 Complex from Rhodobacter sphaeroides. Biochemistry 54:7313-9
Xia, Di; Esser, Lothar; Tang, Wai-Kwan et al. (2013) Structural analysis of cytochrome bc1 complexes: implications to the mechanism of function. Biochim Biophys Acta 1827:1278-94
Qu, Yuan-Gang; Zhou, Fei; Yu, Linda et al. (2013) Effect of mutations of arginine 94 on proton pumping, electron transfer, and superoxide anion generation in cytochrome b of the bc1 complex from Rhodobacter sphaeroides. J Biol Chem 288:1047-54
Su, Ting; Esser, Lothar; Xia, Di et al. (2012) Generation, characterization and crystallization of a cytochrome c(1)-subunit IV fused cytochrome bc(1) complex from Rhodobacter sphaeroides. Biochim Biophys Acta 1817:298-305
Zhou, Fei; Yin, Ying; Su, Ting et al. (2012) Oxygen dependent electron transfer in the cytochrome bc(1) complex. Biochim Biophys Acta 1817:2103-9
Yin, Ying; Yang, Shaoqing; Yu, Linda et al. (2010) Reaction mechanism of superoxide generation during ubiquinol oxidation by the cytochrome bc1 complex. J Biol Chem 285:17038-45
Wang, Qiyu; Yu, Linda; Yu, Chang-An (2010) Cross-talk between mitochondrial malate dehydrogenase and the cytochrome bc1 complex. J Biol Chem 285:10408-14
Yu, Linda; Yang, Shaoqing; Yin, Ying et al. (2009) Chapter 25 Analysis of electron transfer and superoxide generation in the cytochrome bc1 complex. Methods Enzymol 456:459-73
Yin, Ying; Tso, Shih-Chia; Yu, Chang-An et al. (2009) Effect of subunit IV on superoxide generation by Rhodobacter sphaeroides cytochrome bc(1) complex. Biochim Biophys Acta 1787:913-9
Yang, Shaoqing; Ma, He-Wen; Yu, Linda et al. (2008) On the mechanism of quinol oxidation at the QP site in the cytochrome bc1 complex: studied using mutants lacking cytochrome bL or bH. J Biol Chem 283:28767-76

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