Location of the Substrate Binding Site of the Cytochrome bo3 Ubiquinol Oxidase from Escherichia coli

Sylvia K. Choi, Lici Schurig-Briccio, Ziqiao Ding, Sangjin Hong, Chang Sun, Robert B. Gennis

Research output: Contribution to journalArticlepeer-review


Cytochrome bo3 is a respiratory proton-pumping oxygen reductase that is a member of the heme-copper superfamily that utilizes ubiquinol-8 (Q8H2) as a substrate. The current consensus model has Q8H2 oxidized at a low affinity site (QL), passing electrons to a tightly bound quinone cofactor at a high affinity site (QH site) that stabilizes the one-electron reduced ubisemiquinone, facilitating the transfer of electrons to the redox active metal centers where O2 is reduced to water. The current work shows that the Q8 bound to the QH site is more dynamic than previously thought. In addition, mutations of residues at the QH site that do not abolish activity have been re-examined and shown to have properties expected of mutations at the substrate binding site (QL): an increase in the KM of the substrate ubiquinol-1 (up to 4-fold) and an increase in the apparent Ki of the inhibitor HQNO (up to 8-fold). The data suggest that there is only one binding site for ubiquinol in cyt bo3 and that site corresponds to the QH site.

Original languageEnglish (US)
Pages (from-to)8346-8354
Number of pages9
JournalJournal of the American Chemical Society
Issue number24
StatePublished - Jun 21 2017

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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