The oxygen reaction of the cytochrome d-terminated respiratory chain of Escherichia coli at sub-zero temperatures Kinetic resolution by EPR spectroscopy of two high-spin cytochromes

AbstractThe oxygen reaction of the fully reduced respiratory chain in membranes from oxygen-limited Escherichia coli was studied at sub-zero temperatures using EPR spectroscopy. Laser photolysis of CO-liganded cytochrome oxidase d precedes oxidation of at least 2 kinetically separable high-spin cytochromes. At −120 to −100°C, a rhombic signal appears, attributable to cytochrome d, followed at above −100°C, by appearance of a second, axial signal near g = 6, here assigned to cytochrome(s) b, and changes in the redox state of iron-sulphur clusters. The data kinetically resolve the 2 high-spin signals attributed to the oxidase complex and suggest schemes for electron flow to oxygen.Cytochrome oxidase Escherichia coli Cytochrome b-d complexBacterial electron transportLow-temperature techniqu