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. Heterooctamer of two A chains, two B chains, two C chains and two D chains. Increased reduction of the ubiquinone pool (in aerobically grown minimal medium with glucose). Belongs to the cytochrome c oxidase bacterial subunit 4 family. Extended N-terminus.