Title
The CO dehydrogenase accessory protein CooT is a novel nickel-binding protein
Author
Jennifer Timm, Celine Brochier-Armanet, Julien Perard, Barbara Zambelli, Sandrine Ollagnier de Choudens, Stefano Ciurli, Christine Cavazza
Year
2017
Journal
Metallomics
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.
Instrument
J-1500
Keywords
Circular dichroism, Secondary structure, Tertiary structure, Ligand binding, Coordination chemistry, Inorganic chemistry, Biochemistry