Cytochrome bo(3) ubiquinol terminal oxidase is the component of the aerobic respiratory chain of E.coli that predominates when cells are grown at high aeration. Has proton pump activity across the membrane in addition to electron transfer, pumping 2 protons/electron (By similarity). 2 a ubiquinol + n H(+)(in) + O2 = 2 a ubiquinone + n H(+)(out) + 2 H2O Binds 1 copper B ion per subunit. Binds 1 low-spin heme b per subunit. Binds 1 high-spin heme o per subunit. Binds 1 high-affinity quinone that appears to function as a tightly bound cofactor (QH), forming a semiquinone intermediate in the reaction. Heterooctamer of two A chains, two B chains, two C chains and two D chains. Ubiquinol oxidase catalyzes the terminal step in the electron transport chain. Belongs to the heme-copper respiratory oxidase family.