The Cu efflux P-type ATPase CopB and the Cus-like RND system identified herein could contribute to this task.Physiologically, copper is an essential metal ion required as a cofactor for enzymes such as the copper-heme family of cytochrome c oxidases (that also carry Fe???S clusters) and electron transporting blue copper proteins like rusticyanin (5% of the total soluble protein in A. ferrooxidans)