# 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 [NiFe$_3$S$_4$] 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.
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Journal articles
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https://hal.archives-ouvertes.fr/hal-01655185
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Submitted on : Monday, December 4, 2017 - 4:40:03 PM
Last modification on : Tuesday, September 27, 2022 - 4:06:29 AM

### Citation

J. Timm, C. Brochier-Armanet, J. Pérard, B. Zambelli, S. Ollagnier de Choudens, et al.. The CO dehydrogenase accessory protein CooT is a novel nickel-binding protein.. Metallomics, Royal Society of Chemistry, 2017, 9 (5), pp.575-583. ⟨10.1039/c7mt00063d⟩. ⟨hal-01655185⟩

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