CHARACTERIZATION OF THE COPPER CHAPERONE COX17 OF SACCHAROMYCES-CEREVISIAE

Assembly of functional cytochrome oxidase in yeast requires Cox17, whi ch has been postulated to deliver copper ions to the mitochondrion for insertion into the enzyme. This role for Cox17 is supported by the ob servation that it binds copper as a binuclear cuprous-thiolate cluster . X-ray absorption spectroscopy, together with UV-visible absorption a nd emission spectroscopy, indicates the presence of bound cuprous ions , trigonally coordinated by thiolate ligands. Analysis of the EXAFS sh ows three Cu-S bonds at 2.26 Angstrom, plus a short Cu-Cu distance of 2.7 Angstrom, indicating a binuclear cluster in Cox17. The cuprous-thi olate cluster in Cox17 is substantially more labile than structurally related clusters in metallothioneins.