Molecular Basis of Resistance to Inhibitors of the cyt BC1 Complex in Photosynthetic Bacteria
The ubiquinol:cytochrome c oxidoreductase (or the cyt bc 1 complex) is a membrane-bound redox-driven proton pump present in mitochondria of eukaryotes and in many prokaryotes, including photosynthetic bacteria. A similar complex, cyt b 6 f, is also present in plant chloroplasts (1,2,3). During respiration and photosynthesis, these evolutionary well-conserved energy-transducing complexes catalyze electron transfer from lipid soluble quinol derivatives, ubiquinol and plastoquinol, to water soluble electron acceptors, cytochrome c and plastocyanin. in general, they always contain two b-type cytochromes, of different spectroscopic and thermodynamic properties (cyt b L and b H ), carried by a single polypeptide of approximately 40 kDa, a c-type cytochrome of about 30 kDa, and a 2Fe2S cluster containing protein of about 20 kDa (1,3). The structural genes of the three redox-active subunits of the cyt bc 1 complexes of various bacteria have been isolated and their nucleotide sequences have been determined (4,5,6,7). In Rhodobacter capsulatus these three genes are clustered and named fbc (4) or pet (5), with their 5′ to 3′ order being petA (fbcF) (Rieske FeS protein), petB (fbcB) (cyt b) and petC (fbcC) (cyt c 1 ).
KeywordsParacoccus Denitrificans Conserve Histidine Residue Plasmid pRK404 Kink Helix F144L Substitution
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