Cytochrome b558 monitors the steady state redox state of the ubiquinone pool in the aerobic respiratory chain of Escherichia coli.

R. M. Lorence, K. Carter, G. N. Green, R. B. Gennis

Research output: Contribution to journalArticlepeer-review

Abstract

The aerobic respiratory chain of Escherichia coli contains two terminal oxidases, the cytochrome o complex and the cytochrome d complex. These both function as ubiquinol-8 oxidases and reduce molecular oxygen to water. Electron flux is funneled from a variety of dehydrogenases, such as succinate dehydrogenase, through ubiquinone-8, to either of the terminal oxidases. A strain was examined which lacks the intact cytochrome d complex, but which overproduces one of the two subunits of this complex, cytochrome b558. This cytochrome, in the absence of the other subunit of the oxidase complex, does not possess catalytic activity. It is shown that the extent of reduction of cytochrome b558 in the E. coli membrane monitors the extent of reduction of the quinone pool in the membrane. The activity of each purified oxidase was examined in phospholipid vesicles as a function of the amount of ubiquinone-8 incorporated in the bilayer. A ratio of ubiquinol-8:phospholipid as low as 1:200 is sufficient to saturate each oxidase. The maximal turnover of the oxidases in the reconstituted system is considerably faster than observed in E. coli membranes, demonstrating that the rate-limiting step in the E. coli respiratory chain is at the dehydrogenases which feed electrons into the system.

Original languageEnglish (US)
Pages (from-to)10532-10536
Number of pages5
JournalJournal of Biological Chemistry
Volume262
Issue number22
StatePublished - Aug 5 1987
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint

Dive into the research topics of 'Cytochrome b558 monitors the steady state redox state of the ubiquinone pool in the aerobic respiratory chain of Escherichia coli.'. Together they form a unique fingerprint.

Cite this