On the environment of zinc in beef heart cytochrome c oxidase: an x-ray absorption study.

A. Naqui, L. Powers, M. Lundeen, A. Constantinescu, B. Chance

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19 Scopus citations


The role of zinc in beef heart cytochrome c oxidase has been studied by using x-ray absorption spectroscopy, zinc depletion and secondary structure predictions of subunits of beef heart cytochrome c oxidase. The stoichiometry of zinc in cytochrome oxidase has been determined in 35 different preparations and found to be one-half of copper (Cu:Zu = 2:1). Zinc is tightly bound to this enzyme and cannot be removed by dialysis against EDTA. However, zinc could be partially (up to 50%) depleted by treating the enzyme with either dipicolinic acid or by trypsin digestion. This partial depletion of zinc does not change the O2 uptake rate. X-ray absorption spectroscopy shows that the atom is in a distorted tetrahedral environment with mostly sulfur ligands. Since subunit VIa removed by the digestion removes about one-half the zinc, a possible binding site involves the two S sites present in that subunit with an appropriate folding in a structural role.

Original languageEnglish (US)
Pages (from-to)12342-12345
Number of pages4
JournalThe Journal of biological chemistry
Issue number25
StatePublished - Sep 5 1988

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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