title: CopC protein from Pseudomonas syringae: intermolecular transfer of copper from both the copper(I) and copper(II) sites.
abstract: The CopC protein from Pseudomonas syringae pathovar tomato is expressed as one of four proteins encoded by the operon CopABCD that is responsible for copper resistance. It is a small soluble molecule (10.5 kDa) with a beta-barrel structure and features two distinct copper binding sites, which are highly specific for Cu(I) (K(D) > or = 10(-)(13)) and Cu(II) (K(D) approximately 10(-)(15)). These dissociation constants were estimated via ligand competition experiments monitored by electronic spectral and fluorescence probes. The chemistries of the two copper sites are interdependent. When the Cu(II) site is empty, the Cu(I) ion is oxidized by air, but when both sites are occupied, the molecule is stable in air. The availability of an unoccupied site of higher affinity induces intermolecular transfer of either Cu(I) or Cu(II) while maintaining free copper ion concentrations in solution at sub-picomolar levels. This intriguing copper chemistry is consistent with the proposed role of CopC as a copper carrier in the oxidizing periplasmic space. These properties would allow it to exchange either Cu(I) or Cu(II) with its putative partners CopA, CopB, and CopD, contrasting with the role of the Cu(I) (only) chaperones found in the reducing cytoplasm.
authors: School of Chemistry, University of Melbourne, Victoria 3010, Australia.
authors: Melissa
authors: M
authors: Koay
authors: Lianyi
authors: L
authors: Zhang
authors: Binsheng
authors: B
authors: Yang
authors: Megan J
authors: MJ
authors: Maher
authors: Zhiguang
authors: Z
authors: Xiao
authors: Anthony G
authors: AG
authors: Wedd
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D044224:Pseudomonas syringae / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; C071265:CopC protein, Bacteria; D003300:Copper