Siletsky 2017 Biochim Biophys Acta Bioenerg
| Siletsky SA, Belevich I, Belevich NP, Soulimane T, WikstrΓΆm M (2017) Time-resolved generation of membrane potential by ba3 cytochrome c oxidase from Thermus thermophilus coupled to single electron injection into the O and OH states. Biochim Biophys Acta Bioenerg 1858:915-26. https://doi.org/10.1016/j.bbabio.2017.08.007 |
Siletsky SA, Belevich I, Belevich NP, Soulimane T, Wikstroem Marten KF (2017) Biochim Biophys Acta Bioenerg
Abstract: Two electrogenic phases with characteristic times of ~14 ΞΌs and ~290 ΞΌs are resolved in the kinetics of membrane potential generation coupled to single-electron reduction of the oxidized "relaxed" O state of ba3 oxidase from T. thermophilus (OβE transition). The rapid phase reflects electron redistribution between CuA and heme b. The slow phase includes electron redistribution from both CuA and heme b to heme a3, and electrogenic proton transfer coupled to reduction of heme a3. The distance of proton translocation corresponds to uptake of a proton from the inner water phase into the binuclear center where heme a3 is reduced, but there is no proton pumping and no reduction of CuB. Single-electron reduction of the oxidized "unrelaxed" state (OHβEH transition) is accompanied by electrogenic reduction of the heme b/heme a3 pair by CuA in a "fast" phase (~22 ΞΌs) and transfer of protons in "middle" and "slow" electrogenic phases (~0.185 ms and ~0.78 ms) coupled to electron redistribution from the heme b/heme a3 pair to the CuB site. The "middle" and "slow" electrogenic phases seem to be associated with transfer of protons to the proton-loading site (PLS) of the proton pump, but when all injected electrons reach CuB the electronic charge appears to be compensated by back-leakage of the protons from the PLS into the binuclear site. Thus proton pumping occurs only to the extent of ~0.1 H+/e-, probably due to the formed membrane potential in the experiment.
β’ Bioblast editor: Gnaiger E
Labels:
Preparation: Enzyme
Enzyme: Complex IV;cytochrome c oxidase
