Charge Translocation Coupled to Electron Injection into Oxidized Cytochrome c Oxidase from Paracoccus denitrificans

Electrons were discretely injected into oxidized cytochrome c oxidase in liposomes by laser flash excitation of bound ruthenium [II] bispyridyl, and the membrane potential was recorded by time-resolved electrometry. Membrane potential is generated in a fast phase when an electron is transferred from the excited dye, via the CuA center, to heme a at a relative dielectric depth d inside the membrane [Zaslavsky, D., Kaulen, A. D., Smirnova, I. A., Vygodina, T., and Konstantinov, A. A. (1993) FEBS Lett. 336, 389−393]. Subsequently, membrane potential may develop further in a slower event, which is due to proton transfer into the enzyme from the opposite side of the membrane [Ruitenberg, M., Kannt, A., Bamberg, E., Ludwig, B., Michel, H., and Fendler, K. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 4632−4636]. Here, we confirm that injection of the first electron into the fully oxidized cytochrome c oxidase from Paracoccus denitrificans is associated with a fast electrogenic 11 μs phase, but there is no further el...