title: The subunit location of magnesium in cytochrome c oxidase.
abstract: The magnesium ion in bovine heart cytochrome c oxidase can be depleted up to 75% by heat treatment of the enzyme at 43 degrees C followed by dialysis against EDTA buffer solution. The magnesium-depleted enzyme so obtained retains 40% of the activity of the native enzyme. This is the first attempt to deplete magnesium ion from bovine heart cytochrome c oxidase without denaturation of the protein. Magnesium depletion exposes at least one carboxyl group on subunit IV for labeling by N-cyclohexyl-N'-(4-dimethylaminonaphthyl)carbodiimide (NCD-4). The NCD-4 labeling of subunit IV of the magnesium-depleted enzyme is significantly enhanced relative to what is observed for the native and heat-treated oxidase, suggesting that the magnesium ion is located in subunit IV with at least one carboxyl ligand. By comparing the activity of the magnesium-depleted enzyme with that of a control sample of heat-treated oxidase, the influence of divalent magnesium on the activity of the enzyme is assessed.
authors.affiliation: Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena 91125.
authors.forename: J
authors.initials: J
authors.lastname: Lin
authors.forename: L P
authors.initials: LP
authors.lastname: Pan
authors.forename: S I
authors.initials: SI
authors.lastname: Chan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry*; D008274:Magnesium / Q000032:analysis*; D008929:Mitochondria, Heart / Q000201:enzymology; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
chemical_list: D003576:Electron Transport Complex IV; D008274:Magnesium