Potentiometric analysis of the cytochromes of an Escherichia coli mutant strain lacking the cytochrome d terminal oxidase complex

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

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Abstract

A combination of potentiometric analysis and electrochemically poised low-temperature difference spectroscopy was used to examine a mutant strain of Escherichia coli that was previously shown by immunological criteria to be lacking the cytochrome d terminal oxidase. It was shown that this strain is missing cytochromes d, a1, and b558 and that the cytochrome composition of the mutant is similar to that of the wild-type strain grown under conditions of high aeration. The data indicate that the high-aeration branch of the respiratory chain contains two cytochrome components, b556 (midpoint potential [E(m)] = + 35 mV) and cytochrome o (E(m) = + 165 mV). The latter component binds to CO and apparently has a reduced-minus-oxidized split-α band with peaks at 555 and 562 nm. When the wild-type strain was grown under conditions of low aeration, the components of the cytochrome d terminal oxidase complex were observed: cytochrome d (E(m) = + 260 mV), cytochrome a1 (E(m) = + 150 mV) and cytochrome b558 (E(m) = + 180 mV). All cytochromes appeared to undergo simple one-electron oxidation-reduction reactions. In the absence of CO, cytochromes b558 and o have nearly the same E(m) values. In the presence of CO, the E(m) of cytochrome o is raised, thus allowing cytochromes b558 and o to be individually quantitated by potentiometric analysis when they are both present.

Original languageEnglish (US)
Pages (from-to)115-121
Number of pages7
JournalJournal of bacteriology
Volume157
Issue number1
DOIs
StatePublished - 1984

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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