This family consists of several bacterial copper resistance proteins. Copper is essential and serves as cofactor for more than 30 enzymes yet a surplus of copper is toxic and leads to radical formation and oxidation of biomolecules. Therefore, copper homeostasis is a key requisite for every organism. CopB serves to extrude copper when it approaches toxic levels [1].

1: Tetrathiomolybdate inhibition of the Enterococcus hirae CopB copper ATPase. Bissig KD, Voegelin TC, Solioz M; FEBS Lett 2001;507:367-370. PMID:11696373