J. Biol. Chem., Vol. 261, Issue 18, 8104-8107, Jun, 1986
Chemical and spectroscopic evidence for the formation of a ferryl Fea3 intermediate during turnover of cytochrome c oxidase
SN Witt, DF Blair and SI Chan
When partially reduced cytochrome c oxidase samples are reoxidized with
dioxygen, an EPR-silent dioxygen intermediate, which is at the three-
electron level of dioxygen reduction, is trapped at the dioxygen reduction
site. The intermediate has novel spectral features at 580 and 537 nm.
Combined optical and EPR results reveal that this intermediate reacts
rapidly with CO at 277-298 K causing the abolition of the 580/537 mm
features and the appearance of a rhombic CuB EPR signal. A ferryl Fea3, or
an intermediate at the same formal level of oxidation, is proposed to
oxidize CO to CO2 producing an EPR-detectable CuB adjacent to a low-spin
ferrous Fea3-dioxygen (or carbon monoxide) adduct.