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Splitting of the O–O bond at the heme-copper catalytic site of respiratory oxidases

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Poiana Federica, Ballmoos Christoph von, Gonska Nathalie, Blomberg Margareta R. A., Ädelroth Pia, Brzezinski Peter,
Project Functional investigations of bacterial and eukaryotic membrane proteins
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Original article (peer-reviewed)

Journal Sciences Advances
Volume (Issue) 3(6)
Page(s) 1
Title of proceedings Sciences Advances
DOI 10.1126/sciadv.1700279

Open Access

URL https://advances.sciencemag.org/content/3/6/e1700279
Type of Open Access Publisher (Gold Open Access)

Abstract

Heme-copper oxidases catalyze the four-electron reduction of O2 to H2O at a catalytic site that is composed of a heme group, a copper ion (CuB), and a tyrosine residue. Results from earlier experimental studies have shown that the O–O bond is cleaved simultaneously with electron transfer from a low-spin heme (heme a/b), forming a ferryl state (PR; Fe4+=O2−, CuB2+–OH−). We show that with the Thermus thermophilus ba3 oxidase, at low temperature (10°C, pH 7), electron transfer from the low-spin heme b to the catalytic site is faster by a factor of ~10 (τ ≅ 11 μs) than the formation of the PR ferryl (τ ≅110 μs), which indicates that O2 is reduced before the splitting of the O–O bond. Application of density functional theory indicates that the electron acceptor at the catalytic site is a high-energy peroxy state [Fe3+–O−–O−(H+)], which is formed before the PR ferryl. The rates of heme b oxidation and PR ferryl formation were more similar at pH 10, indicating that the formation of the high-energy peroxy state involves proton transfer within the catalytic site, consistent with theory. The combined experimental and theoretical data suggest a general mechanism for O2 reduction by heme-copper oxidases.
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