The crystal structure of the CopC protein from Pseudomonas fluorescens reveals amended classifications for the CopC protein family

Abstract

The bacterial CopC family of proteins are periplasmic copper binding proteins that act in copper detoxification. These proteins contain Cu(I) and/or Cu(II) binding sites, with the family that binds Cu(II) only the most prevalent, based on sequence analyses. Here we present three crystal structures of the CopC protein from Pseudomonas fluorescens (Pf-CopC) that include the wild type protein bound to Cu(II) and two variant proteins, where Cu(II) coordinating ligands were mutated, in Cu-free states. We show that the Cu(II) atom in Pf-CopC is coordinated by two His residues, an Asp residue and the N-terminus of the protein (therefore a 3N + O site). This coordination structure is consistent with..