title: CopK from Cupriavidus metallidurans CH34 binds Cu(I) in a tetrathioether site: characterization by X-ray absorption and NMR spectroscopy.
abstract: Cupriavidus metallidurans CH34 is a bacterium that is resistant to high metal concentrations in the environment. Increased copper resistance is associated with the cop cluster on the large plasmid pMOL30 that is composed of at least 21 genes. The copK gene encodes a 74 residue periplasmic protein whose expression is strongly upregulated in the presence of copper. CopK was previously shown to cooperatively bind Cu(I) and Cu(II) in distinct, specific sites. The solution structure of Cu(I)-CopK and the characterization of the Cu(I) site by X-ray absorption spectroscopy and NMR are reported here. EXAFS spectra are in agreement with a tetrathioether Cu(I) site, providing so far unique spectral information on a 4S-coordinated Cu(I) in a protein. The methionine residues forming the Cu(I) site, M28, M38, M44, and M54, are identified by NMR. We propose the chemical shift of the methionine C(epsilon) as a new and sensitive probe for the detection of Cu(I) bound to thioether groups. The solution structure of Cu(I)-CopK demonstrates that Cu(I) binding induces a complete structural modification with the disruption of the second beta-sheet and a rotation of the C-terminal part of nearly 180 degrees around a hinge formed by asparagine 57. This conformational change is directly related to the loss of the dimer interface and most probably to the formation of the Cu(II) site involving histidine 70. The solution structure of Cu(I)-CopK therefore provides the molecular basis for the understanding of the Cu(I)/Cu(II) binding cooperativity.
authors.affiliation: Environmental Geochemistry Group, LGIT, UMR 5559, Université Joseph Fourier and CNRS, BP 53, 38041 Grenoble, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Sarret
authors.forename: Adrien
authors.initials: A
authors.lastname: Favier
authors.forename: Jacques
authors.initials: J
authors.lastname: Covès
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Hazemann
authors.forename: Max
authors.initials: M
authors.lastname: Mergeay
authors.forename: Beate
authors.initials: B
authors.lastname: Bersch
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D049921:Cupriavidus; D004986:Ether / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D012996:Solutions; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D012996:Solutions; C065826:cop protein, Bacteria; D004986:Ether; D003300:Copper