Characterization of the interaction between the Wilson and Menkes disease proteins and the cytoplasmic copper chaperone, HAH1p

Wilson disease (WD) and Menkes disease (MNK) are inherited disorders of cop per metabolism. The genes that mutate to give rise to these disorders encod e highly homologous copper transporting ATPases, We use yeast and mammalian two-hybrid systems, along with an in vitro assay to demonstrate a specific , copper-dependent interaction between the six metal-binding domains of the WD and MNK ATPases and the cytoplasmic copper chaperone HAH1, We demonstra te that several metal-binding domains interact independently or in combinat ion with HAH1p, although notably domains five and six of WDp do not. Altera tion of either the Met or Thr residue of the HAH1p MTCXXC motif has no obse rvable effect on the copper-dependent interaction, whereas alteration of ei ther of the two Cys residues abolishes the interaction. Mutation of any one of the HAH1p C-terminal Lys residues (Lys(56), Lys(57), or Lys(60)) to Gly does not affect the interaction, although deletion of the 15 C-terminal re sidues abolishes the interaction. We show that apo-HAH1p can bind in vitro to copper-loaded WDp, suggesting reversibility of copper transfer from HAH1 p to WD/MNKp. The in vitro HAH1/WDp interaction is metalospecific; HAH1 pre incubated with Cu2+ or Hg+ but not with Zn2+, Cd2+, Co2+, Ni3+, Fe3+, or Cr 3+ interacted with WDp, Finally, we model the protein-protein interaction a nd present a theoretical representation of the HAH1p Cu WD/MNKp complex.