Metal selectivity in P_(1B)-type ATPase transporters is determined by conserved amino acid residues in their transmembrane helices responsible for metal binding and transport across the cellular membrane. The Cu^(2+)-selective CopB from Archaeoglobus fulgidus has been investigated to explore the coordination chemistry of the transition metal binding sites in P_(1B-3)-type ATPases. Electronic absorption, electron paramagnetic resonance, and X-ray absorption spectroscopic studies indicate the presence of a high-affinity transmembrane Type-2-like Cu^(2+) center in which a single cupric ion is coordinated in a distorted square pyramidal geometry by mixed nitrogen/oxygen and sulfur ligands
