An NMR Study of the Interaction of the N-terminal Cytoplasmic Tail of the Wilson Disease Protein with Copper(I)-HAH1

ATP7B is a human P-1B-type ATPase that has a crucial role in maintaining copper(I) homeostasis. Mutations in the corresponding gene are the cause of Wilson disease. Among its various distinguishing features is a long (similar to 630 amino acids) N-terminal cytosolic tail containing six domains that are individually folded and capable of binding one copper(I) ion each. We expressed the entire tail as a single construct in Escherichia coli and investigated its interaction with its copper chaperone (i.e. HAH1) by solution NMR spectroscopy. We observed that all six of the metal-binding domains were metallated by Cu(I)-HAH1, with the first, the second, and the fourth domains forming an adduct with it. This behavior is different from that of the highly similar human ATPase ATP7A, in which only two domains form such an adduct. The distinct behaviors of the different domains were analyzed in terms of the energetics of Cu(I) transfer, hinting at a specific role of the interaction with copper(I)-HAH1 in the overall functional process.