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Issue 5, 2017
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The CO dehydrogenase accessory protein CooT is a novel nickel-binding protein

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Abstract

In Rhodospirillum rubrum, maturation of Carbon Monoxide Dehydrogenase (CODH) requires three accessory proteins, CooC, CooT and CooJ, dedicated to nickel insertion into the active site, which is constituted by a distorted [NiFe3S4] cubane coordinated with a mononuclear Fe site. CooC is an ATPase proposed to provide the energy required for the maturation process, while CooJ is described as a metallochaperone with 16 histidines and 2 cysteines at the C-terminus, likely involved in metal binding and/or storage. Prior to the present study, no information was available on CooT at the molecular level. Here, the X-ray structure of RrCooT was obtained, which revealed that this protein is a homodimer featuring a fold that resembles an Sm-like domain, suggesting a role in RNA metabolism that was however not supported by experimental observations. Biochemical and biophysical evidence based on circular dichroism spectroscopy, light scattering, isothermal titration calorimetry and site-directed mutagenesis showed that RrCooT specifically binds a single Ni(II) per dimer, with a dissociation constant of 9 nM, through the pair of Cys2, highly conserved residues, located at the dimer interface. Despite its role in the activation of RrCODH in vivo, CooT was thought to be a unique protein, found only in R. rubrum, with an unclear function. In this study, we extended the biological impact of CooT, establishing that this protein is a member of a novel Ni(II)-binding protein family with 111 homologues, linked to anaerobic metabolism in bacteria and archaea, and in most cases to the presence of CODH.

Graphical abstract: The CO dehydrogenase accessory protein CooT is a novel nickel-binding protein

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Publication details

The article was received on 04 Mar 2017, accepted on 10 Apr 2017 and first published on 18 Apr 2017


Article type: Paper
DOI: 10.1039/C7MT00063D
Citation: Metallomics, 2017,9, 575-583
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    The CO dehydrogenase accessory protein CooT is a novel nickel-binding protein

    J. Timm, C. Brochier-Armanet, J. Perard, B. Zambelli, S. Ollagnier-de-Choudens, S. Ciurli and C. Cavazza, Metallomics, 2017, 9, 575
    DOI: 10.1039/C7MT00063D

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