Abstract
The functional significance of the metal centres of cytochrome oxidase is deduced from the ways in which the centres are bound into its peptides. To this end use is made of structural knowledge of other metallo-proteins for dioxygen binding, haemocyanin and haemoglobin, and for electron transfer, cytochromes b and azurin. The order and manner in which the motions of helical sections of the oxidase are linked to proton pumping are suggested and a comparison is made with other proton pumps, for example that of ATP synthetases.