Functional design of bacterial superoxide:quinone oxidoreductase

Abou-Hamdan, Abbas; Mahler, Roman; Grossenbacher, Philipp; Biner, Olivier; Sjöstrand, Dan; Lochner, Martin; Högbom, Martin; von Ballmoos, Christoph (23 December 2021). Functional design of bacterial superoxide:quinone oxidoreductase (bioRxiv). Cold Spring Harbor Laboratory 10.1101/2021.12.23.473985

2021.12.23.473985v1.full.pdf - Published Version
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The superoxide anion - molecular oxygen reduced by a single electron - is produced in large amounts by enzymatic and adventitious reactions and can perform a range of cellular functions, including bacterial warfare and iron uptake, signalling and host immune response in eukaryotes. However, it also serves as precursor for more deleterious species such as the hydroxyl anion or peroxynitrite and therefore, cellular defense mechanisms for superoxide neutralization have evolved. In addition to the soluble proteins superoxide dismutase and superoxide reductase, recently the membrane embedded diheme cytochrome b561(CybB) from E. coli has been proposed to act as a superoxide:quinone oxidoreductase. Here, we confirm superoxide and cellular ubiquinones or menaquinones as natural substrates and show that quinone binding to the enzyme accelerates the reaction with superoxide. The reactivity of the substrates is in accordance with the here determined midpoint potential of the two b hemes (+48 and -23 mV / NHE). Our data suggest that the enzyme can work near the diffusion limit in the forward direction and can also catalyse the reverse reaction efficiently under physiological conditions. The data is discussed in context of described cytochrome b561 proteins and potential physiological roles of CybB.

Item Type:

Working Paper


04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine
08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)

Graduate School:

Graduate School for Cellular and Biomedical Sciences (GCB)

UniBE Contributor:

Abou Hamdan, Abbas Maxime, Mahler, Roman Alois, Grossenbacher, Philipp, Biner, Olivier Felix, Lochner, Martin, von Ballmoos, Christoph


500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry
600 Technology > 610 Medicine & health




Cold Spring Harbor Laboratory




Martin Lochner

Date Deposited:

18 Mar 2024 14:27

Last Modified:

18 Mar 2024 14:27

Publisher DOI:





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