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Article

Copper-Induced Conformational Changes in the N-Terminal Domain of the Wilson Disease Copper-Transporting ATPase^†

Michael DiDonato,^‡^§ Hua-Fen Hsu, Suree Narindrasorasak,^‡ Lawrence Que, Jr.,* and Bibudhendra Sarkar*^‡^§

Department of Structural Biology and Biochemistry, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada, Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada, and Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455

Biochemistry, 2000, 39 (7), pp 1890–1896

DOI: 10.1021/bi992222j

Publication Date (Web): January 25, 2000

†

This work was supported by grants from the Medical Research Council of Canada (MOP-1800) and the U.S. National Science Foundation (DMB9808350).

‡

The Hospital for Sick Children.

University of Toronto.

Current address: Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037.

University of Minnesota.

Corresponding authors.

Abstract

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 followed by extensive tissue damage and death. The ATPase has a novel amino-terminal domain (70 kDa) which contains six repeats of the copper binding 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 spectroscopy (XAS) has revealed that each binding site ligates copper in the +1 oxidation state using two cysteine side chains with distorted linear geometry. Analysis of copper-induced conformational changes in the amino-terminal domain indicates that both secondary and tertiary structure changes take place upon copper binding. These copper-induced conformational changes could play an important role in the function and regulation of the ATPase in vivo. In addition to providing important insights on copper binding to the protein, these results suggest a possible mechanism of copper trafficking by the Wilson disease ATPase.