Thebc
1 complexes ofRhodobacter sphaeroides andRhodobacter capsulatus |
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Authors: | Robert B Gennis Blanca Barquera Beth Hacker Steven R Van Doren Sylvain Arnaud Antony R Crofts Edgar Davidson Kevin A Gray Fevzi Daldal |
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Institution: | (1) School of Chemical Sciences, University of Illinois, 61801 Urbana, Illinois;(2) School of Life Sciences, University of Illinois, 61801 Urbana, Illinois;(3) Department of Biology, Plant Science Institute, University of Pennsylvania, 19104 Philadelphia, Pennsylvania;(4) Present address: Biophysics Research Division, University of Michigan, 2200 Bonisteel Blvd., 48109-2099 Ann Arbor, Michigan |
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Abstract: | Photosynthetic bacteria offer excellent experimental opportunities to explore both the structure and function of the ubiquinol-cytochromec oxidoreductase (bc
1 complex). In bothRhodobacter sphaeroides andRhodobacter capsulatus, thebc
1 complex functions in both the aerobic respiratory chain and as an essential component of the photosynthetic electron transport chain. Because thebc
1 complex in these organisms can be functionally coupled to the photosynthetic reaction center, flash photolysis can be used to study electron flow through the enzyme and to examine the effects of various amino acid substitutions. During the past several years, numerous mutations have been generated in the cytochromeb subunit, in the Rieske iron-sulfur subunit, and in the cytochromec
1 subunit. Both site-directed and random mutagenesis procedures have been utilized. Studies of these mutations have identified amino acid residues that are metal ligands, as well as those residues that are at or near either the quinol oxidase (Qo) site or the quinol reductase (Qi) site. The postulate that these two Q-sites are located on opposite sides of the membrane is supported by these studies. Current research is directed at exploring the details of the catalytic mechanism, the nature of the subunit interactions, and the assembly of this enzyme. |
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Keywords: | Cytochrome bc
1 complex III Q-cycle photosynthesis |
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