Inactive, lipid-depleted cytochrome oxidase was rapidly activated upon incubation with either neutral, basic, or acidic liposomes. When incubated with 0.5 to 10 times its weight in liposomes, the enzyme bound 20% of its weight in lipids. This amount of bound lipids probably corresponds to the “annular lipids” postulated to be tightly bound to cytochrome oxidase (Jest, P. C., Griffith, 0. H., Ca...