Bovine heart cytochrome c oxidase preparations contain high affinity binding sites for magnesium as well as for zinc, copper, and heme iron.
Metal contents of six bovine heart cytochrome c oxidase preparations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Magnesium is present in consistent amounts reflected by Fe/Mg and Mg/Zn ratios of 2.06 +/- 0.18 and 1.10 +/- 0.14, respectively. More copper than iron is always present; the average Cu/Fe atom ratio is 1.27 +/- 0.10. Calcium is found in significant but variable amounts. Mg, Zn, Fe, and Cu are each bound with high affinity as shown by a resistance to removal upon dialysis against various media. The Cu in excess of Fe, the Mg, and the Zn may each have catalytic and/or structural roles in the oxidase. The observed metal stoichiometry suggests that a dimeric catalytic unit with 5 Cu, 4 Fe, 2 Zn, and 2 Mg may be present in the inner mitochondrial membrane to carry out O2 reduction and H+ pumping.
Einarsdóttir
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Caughey
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D000818:Animals; D002417:Cattle; D003300:Copper / Q000378:metabolism; D003956:Dialysis; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008670:Metals / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology*; D013054:Spectrophotometry, Atomic; D015032:Zinc / Q000378:metabolism
D008670:Metals; D006418:Heme; D003300:Copper; D007501:Iron; D003576:Electron Transport Complex IV; D008274:Magnesium; D015032:Zinc