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 β-barrel structure and features two distinct copper binding sites, which are highly specific for CuI (KD ≥ 10-13) and CuII (KD ≈ 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 CuII 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 a..