Purification and properties of two terminal oxidase complexes of Escherichia coli aerobic respiratory chain.
Two terminal oxidase complexes, cytochrome b-562-o complex and cytochrome b-558-d complex, are isolated in highly purified forms which show ubiquinol oxidase activities. From the result of steady-state kinetics of cytochromes in the membrane and E'm values of purified cytochromes, we propose a branched arrangement of the late exponential phase of aerobic growth, as shown in Fig. 10. Cytochrome b-556 is reduced by several dehydrogenases and the gene for this cytochrome (cybA) is located in the sdh gene cluster. Recently, we found another low-potential b-type cytochrome, cytochrome b-561 (Em' = 20 mV), which is also reduced by dehydrogenases. The position of this new cytochrome in the aerobic respiratory chain is under investigation. Two terminal oxidase complexes branch at the site of ubiquinone-8, and the Km value for oxygen of the purified cytochrome b-558-d complex is about 8-fold lower than that of the purified cytochrome b-562-o complex when ubiquinol-1 is used as substrate. This result is consistent with the idea that the cytochrome b-558-d complex is synthesized as an alternative oxidase for more efficient utilization of oxygen at low oxygen concentration. Thus, E. coli cells can maintain efficient oxidative energy conservation over a wide range of oxygen pressures by simply changing the contents of the two terminal oxidases, each of which functions as a coupling site.
Kita
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Konishi
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Anraku
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D002462:Cell Membrane / Q000201:enzymology; D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D003573:Cytochrome b Group / Q000302:isolation & purification* / Q000378:metabolism; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D003576:Electron Transport Complex IV / Q000302:isolation & purification* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D007700:Kinetics; D019255:NADPH Oxidases; D010088:Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D010101:Oxygen Consumption
D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; C036888:cytochrome b558; C017850:cytochrome b562, E coli; D010088:Oxidoreductases; D019255:NADPH Oxidases; C040077:cytochrome bd terminal oxidase complex, E coli; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV