Fig. 2. Cu⁺ transport pathway.

(A and B) Two views of the presumed Cu⁺ transport pathway. Critical residues lining the Cu⁺ permeation path from the cytosol to the lumen are highlighted. The dashed line indicates the approximate Cu⁺ path in (A). The cytoplasmic Cu⁺ entry site is highlighted in (B). The invariant CPC motif is indicated. Pore calculation indicates that the Cu⁺ exit pathway is accessible from the luminal side (E2-Pi state). Surface electrostatic potential (red, −5 kT/e; white, neutral; and blue, +5 kT/e) is viewed from the luminal side.