Dynamics of the KB Proton Pathway in Cytochrome ba3 from Thermus thermophilus

Christoph von Ballmoos, Irina Smirnova, Federica Poiana, Nathalie Gonska, Hsin Yang Chang, Robert B. Gennis, Peter Brzezinski, Pia Ädelroth*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The ba3 cytochrome c oxidase from Thermus thermophilus is a B-type oxygen-reducing heme-copper oxidase and a proton pump. It uses only one proton pathway for transfer of protons to the catalytic site, the KB pathway. It was previously shown that the ba3 oxidase has an overall similar reaction sequence to that in mitochondrial-like A-type oxidases. However, the timing of loading the pump site, and formation and decay of catalytic intermediates is different in the two types of oxidases. In the present study, we have investigated variants in which two amino acids of the KB proton pathway leading to the catalytic site were exchanged; Tyr-248 (located ∼23 Å below the active site towards the cytoplasm) in subunit I (Y248T) and Glu-15 (∼26 Å below the active site, ∼16 Å from Tyr-248) in subunit II (E15IIQ). Even though the overall catalytic turnover in these two variants is similar and very low (<1 % of wildtype), the substitutions had distinctly different effects on the kinetics of proton transfer to the catalytic site. The results indicate that the Glu-15II is the only essentially crucial residue of the KB pathway, but that the Tyr-248 also plays a distinct role in defining an internal proton donor and controlling the dynamics of proton transfer to the pump site and the catalytic site.

Original languageEnglish
Pages (from-to)424-436
Number of pages13
JournalIsrael Journal of Chemistry
Issue number5
StatePublished - 1 May 2017


  • cytochrome aa
  • cytochrome c oxidase
  • cytochrome cbb
  • electron transfer
  • heme-copper oxidases
  • membrane protein
  • metalloprotein
  • proton transfer
  • redox reaction
  • respiration


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