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

Abstract

In Rhodospirillum rubrum, the maturation of Carbon Monoxide Dehydrogenase (CODH) requires three accessory proteins, CooC, CooT and CooJ, dedicated to nickel insertion into the active site, constituted of a distorted [NiFe3S4] cubane coordinated to a mononuclear Fe site. CooC is an ATPase proposed to provide the energy required for the maturation proces s, 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 and revealed that this protein is a homodimer featuring a fold that resembles a Sm-like domain, suggesting a role in RNA metabolism that was otherwise not supported by experimental observations. Biochemical and biophysical evidences based on circular dichroism spectroscopy, light scattering, isothermal titration calorimetry and site-directed mutagenesis showed that RrCooT binds specifically a single Ni(II) per dimer, with a dissociation constant of 9 nM, through the pair of Cys2, a highly conserved residue, 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.

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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, Accepted Manuscript
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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, Accepted Manuscript , DOI: 10.1039/C7MT00063D

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