Bacterial CytochromecOxidase

Further Insights into the Spectroscopic Properties, Electronic Structure, and Kinetics of Formation of the Heme−Peroxo−Copper Complex [(F8TPP)FeIII−(O22-)−CuII(TMPA)]+

“…Confirming earlier biochemical and molecular biological suppositions are the recent X-ray crystallographic studies which show that dioxygen reduction occurs at an active site consisting of a heme a 3 -Cu B heterobinuclear center with an intermetal separation of 4.5−5.2 Å, depending on the protein derivative (Figure ). − As it is generally considered, dioxygen binding and reduction occurs as follows: ,− An initial Cu B −O 2 interaction precedes transfer of O 2 to heme a 3 , forming a ferrous−oxy (Fe III −superoxo) observable intermediate ( A ). The next intermediate detected has already undergone O−O cleavage, giving the ferryl Fe IV O species ( P ) and Cu B II −OH, with either tyrosinate or tyrosyl radical (Tyr • ), depending on the enzyme form used for the O 2 -chemistry.…”

“…As a member of the heme−copper oxidase superfamily, cytochrome c oxidase (C c O) utilizes electrons provided sequentially by cytochrome c to catalyze the 4e - /4H + reduction of dioxygen to water. − This membrane-bound multimetallic enzyme couples this exergonic process to the movement of four additional protons across the mitochondrial membrane, resulting in a net translocation of four charges. The proton pumping mechanism of C c O generates the membrane potential used by ATP synthase to drive the formation of ATP from ADP, and in light of its biologically important relevance, has been the subject of numerous and intense biophysical and spectroscopic investigations.…”