A review of published experimental and interpretative knowledge concerning proton ejection associated with cytochrome c oxidation by artificial phospholipid vesicles inlaid with cytochrome c oxidase indicates that the detailed characteristics of the redox-linked proton ejection cannot be simply explained by proton pumping. We propose an alternative hypothesis according to which proton ejection is due to the redoxlinked deprotonation of a complex involving phospholipid and cytochrome c at the surface of the vesicles. The postulates upon which this hypothesis depends are explicitly outlined, and some methods of testing the hypothesis are suggested.
