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 Title: Molecular genetic studies on the cytochrome bc(1) complex of Rhodobacter sphaeroides Author(s): Yun, Chang-Hyon Doctoral Committee Chair(s): Gennis, Robert B. Department / Program: Biophysics and Computational Biology Discipline: Biophysics Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Biology, Molecular Biophysics, General Abstract: The ubiquinol:cytochrome c$\sb2$ oxidoreductase ($bc\sb1$ complex) is a central component of the mitochondrial respiratory chain as well as the respiratory and photosynthetic system of many prokaryotes. The fact that the $bc\sb1$ complex from Rb. sphaeroides has been extensively studied, plus the ability to genetically manipulate this organism, makes this an ideal system for site-directed mutagenesis to address questions relating to the structure and function of the $bc\sb1$ complex.In this thesis, the cloning and complete sequence of the fbc operon from Rb. sphaeroides is reported. As in other bacteria, this operon contains three genes, encoding the Rieske FeS subunit, the cytochrome b subunit, and the cytochrome $c\sb1$ subunit. Recombination techniques were used to delete the fbc operon from the chromosome, resulting in strains that are incapable of growing photosynthetically. Photosynthetic growth is restored by complementing in trans by the fbc operon on a plasmid.The topology of the b cytochrome subunit has been tested by constructing the fbcB-phoA gene fusions. The results of the fusion were consistent with the eight-span model that has recently been widely accepted.The main focus of this thesis is the structure and function relationship of the b cytochrome subunit studied by site-directed mutagenesis of a number of highly conserved amino acid residues. It is shown that the four histidines that are conserved in all the b cytochromes are essential residues for the functioning of the complex, and probably are the ligands for the two b hemes. Strains carrying mutations on these histidines have lost either both b hemes or the high-potential b heme. In addition, several of highly conserved amino acids, e.g. Gly-48, Gln-58, Ser-102, Phe-104, and Pro-202, whose probable importance had previously been suggested, were altered and the resulting strains were characterized. Issue Date: 1990 Type: Text Language: English URI: http://hdl.handle.net/2142/21737 Rights Information: Copyright 1990 Yun, Chang-Hyon Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9026364 OCLC Identifier: (UMI)AAI9026364
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