PMID:2856144
| Citation |
Kita, K, Konishi, K and Anraku, Y (1986) Purification and properties of two terminal oxidase complexes of Escherichia coli aerobic respiratory chain. Meth. Enzymol. 126:94-113 |
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| Abstract |
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. |
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| Keywords |
Cell Membrane/enzymology; Chromatography, Gel/methods; Chromatography, Ion Exchange/methods; Cytochrome b Group/isolation & purification; Cytochrome b Group/metabolism; Cytochromes; Electron Transport Chain Complex Proteins; Electron Transport Complex IV/isolation & purification; Electron Transport Complex IV/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Kinetics; NADPH Oxidase; Oxidoreductases/isolation & purification; Oxidoreductases/metabolism; Oxygen Consumption |
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