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Why copper is preferred over iron for oxygen activation and reduction in haem-copper oxidases

Nature Chemistry volume 9, pages 257–263 (2017)Cite this article

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Abstract

Haem–copper oxidase (HCO) catalyses the natural reduction of oxygen to water using a haem-copper centre. Despite decades of research on HCOs, the role of non-haem metal and the reason for nature's choice of copper over other metals such as iron remains unclear. Here, we use a biosynthetic model of HCO in myoglobin that selectively binds different non-haem metals to demonstrate 30-fold and 11-fold enhancements in the oxidase activity of Cu- and Fe-bound HCO mimics, respectively, as compared with Zn-bound mimics. Detailed electrochemical, kinetic and vibrational spectroscopic studies, in tandem with theoretical density functional theory calculations, demonstrate that the non-haem metal not only donates electrons to oxygen but also activates it for efficient O–O bond cleavage. Furthermore, the higher redox potential of copper and the enhanced weakening of the O–O bond from the higher electron density in the d orbital of copper are central to its higher oxidase activity over iron. This work resolves a long-standing question in bioenergetics, and renders a chemical–biological basis for the design of future oxygen-reduction catalysts.

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Figure 1: Structure and function of FeBMb variants.
Figure 2: Electrochemical, spectroscopic and kinetic investigation of FeBMb variants.

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Acknowledgements

We thank A. R. Damodaran and R. B. Gennis for helpful comments and suggestions on the manuscript. We also thank P. Hosseinzadeh, M. R. Sponholtz and S. Dwaraknath for help with various aspects of data collection and analysis. J. R. was supported by a predoctoral training grant 5T32-GM070421 from the US National Institute of Health. This material is based on work supported by the US National Institutes of Health (NIH) under Award NIH R01GM06211 (to Y.L.) and NIH R01GM074785 (to P.M.-L.) and by a US National Science Foundation (NSF) Award (NSF CHE-1300912 to Y.Z.). Use of the Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract no. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the Department of Energy Office of Biological and Environmental Research, and by the NIH National Institute of General Medical Sciences (NIGMS) (including P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH.

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Authors and Affiliations

  1. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

    Ambika Bhagi-Damodaran, Braddock A. Sandoval, Saumen Chakraborty & Yi Lu

  2. Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology, Hoboken, New Jersey, USA

    Matthew A. Michael & Yong Zhang

  3. Division of Environmental & Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon, USA

    Qianhong Zhu & Pierre Moënne-Loccoz

  4. Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

    Julian Reed & Yi Lu

  5. Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

    Evan N. Mirts & Yi Lu

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  1. Ambika Bhagi-Damodaran
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Contributions

A.B.-D. and Y.L. designed the research. A.B.-D., J.R. and B.A.S. purified and characterized the proteins, performed the oxygen-reduction assays, and the electrochemical, EPR and stopped-flow experiments. E.M. performed the XANES study and analysed the data. S.C. helped with the initial assay design, M.A.M. and Y.Z. performed the DFT calculations and Q.Z. and P.M.-L. performed the RR experiments. A.B.D. Y.Z., P.M.-L. and Y.L. wrote the paper. All the authors contributed to developing the rationale of the manuscript and analysis of results.

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Correspondence to Pierre Moënne-Loccoz, Yong Zhang or Yi Lu.

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Bhagi-Damodaran, A., Michael, M., Zhu, Q. et al. Why copper is preferred over iron for oxygen activation and reduction in haem-copper oxidases. Nature Chem 9, 257–263 (2017). https://doi.org/10.1038/nchem.2643

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