Copper-induced conformational changes in the N-terminal domain of the Wilson disease copper-transporting ATPase

The Wilson disease copper-transporting ATPase plays a critical role in the intracellular trafficking of copper. Mutations in this protein lead to the accumulation of a toxic level of copper in the liver, kidney, and brain fol lowed by extensive tissue damage and death. The ATPase has a novel aminoter minal domain (similar to 70 kDa) which contains six repeals of the copper b inding motif GMTCXXC. We have expressed and characterized this domain with respect to the copper binding sites and the conformational consequences of copper binding. A detailed analysis of this domain by X-ray absorption spec troscopy (XAS) has revealed that each binding site ligates copper in the +1 oxidation state using two cysteine side chains with distorted linear geome try. Analysis of copper-induced conformational changes in the aminoterminal domain indicates that both secondary and tertiary structure changes take p lace upon copper binding. These copper-induced conformational changes could play an important role in the function and regulation of the ATPase in viv o. In addition to providing important insights on copper binding to the pro tein, these results suggest a possible mechanism of copper trafficking by t he Wilson disease ATPase.