Time-resolved single-turnover of caa3 oxidase from Thermus thermophilus. Fifth electron of the fully reduced enzyme converts OH into EH state

Sergey A. Siletsky, Ilya Belevich, Nikolai P. Belevich, Tewfik Soulimane, Michael I. Verkhovsky

Research output: Contribution to journalArticlepeer-review

Abstract

The oxidative part of the catalytic cycle of the caa3-type cytochrome c oxidase from Thermus thermophilus was followed by time-resolved optical spectroscopy. Rate constants, chemical nature and the spectral properties of the catalytic cycle intermediates (Compounds A, P, F) reproduce generally the features typical for the aa3-type oxidases with some distinctive peculiarities caused by the presence of an additional 5-th redox-center-a heme center of the covalently bound cytochrome c. Compound A was formed with significantly smaller yield compared to aa3 oxidases in general and to ba3 oxidase from the same organism. Two electrons, equilibrated between three input redox-centers: heme a, CuA and heme c are transferred in a single transition to the binuclear center during reduction of the compound F, converting the binuclear center through the highly reactive OH state into the final product of the reaction-E H (one-electron reduced) state of the catalytic site. In contrast to previous works on the caa3-type enzymes, we concluded that the finally produced EH state of caa3 oxidase is characterized by the localization of the fifth electron in the binuclear center, similar to the OH → EH transition of the aa3-type oxidases. So, the fully-reduced caa3 oxidase is competent in rapid electron transfer from the input redox-centers into the catalytic heme-copper site.

Original languageEnglish
Pages (from-to)1162-1169
Number of pages8
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1807
Issue number9
DOIs
Publication statusPublished - Sep 2011

Keywords

  • Catalytic cycle intermediates
  • Cytochrome c oxidase
  • Electron transfer
  • Thermus thermophilus

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