In silico modeling of the Menkes copper-translocating P-type ATPase 3rd metal binding domain predicts that...

The Menkes (ATP7A) P(1B)-type ATPase is a transmembrane copper-translocating protein. It contains six similar high-affinity metal-binding domains (MBDs) in the N-terminal cytoplasmic tail that are important for sensing intracellular copper and regulating ATPase function through the transfer of copper between domains. Molecular characterization of copper-binding and transfer is predominantly dependent on NMR structures derived from E. coli expression systems. A limitation of these models is the exclusion of post-translational modifications. We have previously shown that the third copper-binding domain, MBD3, uniquely contains two phosphorylated residues: Thr-327, which is phosphorylated only in the presence of elevated copper; and Ser-339, which is constitutively phosphorylated independent of copper levels. Here, using molecular dynamic simulations, we have incorporated these phosphorylated residues into a model based on the NMR structures of MBD3. Our data suggests that constitutively phosphorylated Ser-339, which is in a loop facing the copper-binding site, may facilitate the copper transfer process by exposing the CxxC copper-binding region of MBD3. Copper-induced phosphorylation of Thr327 is predicted to stabilize this change in conformation. This offers new molecular insights into how cell signaling (phosphorylation) can affect MBD structure and dynamics and how this may in turn affect copper-binding and thus copper-translocation functions of ATP7A.