Cytochrome bo is a member of the heme-copper terminal oxidase superfamily and serves as
a four-subunit ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli. To
probe the location and structural properties of the ubiquinol oxidation site, we isolated and
characterized five or 10 spontaneous mutants resistant to either 2, 6-dimethyl-1, 4-
benzoquinone, 2, 6-dichloro-4-nitrophenol, or 2, 6-dichloro-4-dicyanovinylphenol, the potent
competitive inhibitors for the oxidation of ubiquinol-1 [Sato-Watanabe, M., Mogi, T., Miyoshi …