Escherichia coli is known to couple aerobic respiratory catabolism to ATP synthesis by virtue of the primary generators of the proton motive force - NADH dehydrogenase I, cytochrome bo 3, and cytochrome bd-I. An E. coli mutant deficient in NADH dehydrogenase I, bo 3 and bd-I can, nevertheless, grow aerobically on nonfermentable substrates, although its sole terminal oxidase cytochrome bd-II has been reported to be nonelectrogenic. In the current work, the ability of cytochrome bd-II to generate a proton motive force is reexamined. Absorption and fluorescence spectroscopy and oxygen pulse methods show that in the steady-state, cytochrome bd-II does generate a proton motive force with a H +/e - ratio of 0.94 ± 0.18. This proton motive force is sufficient to drive ATP synthesis and transport of nutrients. Microsecond time-resolved, single-turnover electrometry shows that the molecular mechanism of generating the proton motive force is identical to that in cytochrome bd-I. The ability to induce cytochrome bd-II biosynthesis allows E. coli to remain energetically competent under a variety of environmental conditions.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Oct 18 2011|
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