Wilson's disease is an autosomal recessive human illness in which large quantities of copper accumulate in various organs, including the brain and the liver. If left untreated, it results in hepatitis, neurological complications, and death. Long-Evans Cinnamon (LEC) rats have a homologous mutation to Wilson's disease and thus provide an animal model. Liver lysosomes from tetrathiomolybdate-treated LEC rats were isolated and analyzed by Cu and Mo K-edge X-ray absorption spectroscopy. The lysosomes contained a Cu-Mo-S cluster in which the Mo is coordinated by four sulfurs at 2.24 A with approximately three copper neighbors at 2.70 A. Each Cu is coordinated to 3-4 sulfurs at 2.28 A with approximately one Mo neighbor at 2.70 A. These results indicate the formation of a biologically novel molybdenum-copper-sulfur cluster. ; Graham N. George, Ingrid J. Pickering, Hugh H. Harris, Jürgen Gailer, Dominik Klein, Josef Lichtmannegger, and Karl-Heinz Summer ; Copyright © 2003 American Chemical Society