Copper-transporting P-type ATPases use a unique ion-release pathway

Heavy metals in cells are typically regulated by P-IB-type ATPases. The first structure of the class, a Cu+-ATPase from Legionella pneumophila (LpCopA), outlined a copper transport pathway across the membrane, which was inferred to be occluded. Here we show by molecular dynamics simulations that extracellular water solvated the transmembrane (TM) domain, results indicative of a Cu+-release pathway. Furthermore, a new LpCopA crystal structure determined at 2.8-angstrom resolution, trapped in the preceding E2P state, delineated the same passage, and site-directed-mutagenesis activity assays support a functional role for the conduit. The structural similarities between the TM domains of the two conformations suggest that Cu+-ATPases couple dephosphorylation and ion extrusion differently than do the well-characterized P-II-type ATPases. The ion pathway explains why certain Menkes' and Wilson's disease mutations impair protein function and points to a site for inhibitors targeting pathogens.