This is a schematic representation of the CusA channel. The conserved residues R83, E567, D617, E625, R669 and K678, lining the channel at the periplasmic domain are indicated. The dotted red circle marks the location of the Cu(I) binding site formed by the methionine triad M573, M623 and M672. The paths for metal transport through the periplasmic cleft and transmembrane region are illustrated with black curves.