TY - JOUR
T1 - Time-resolved generation of membrane potential by ba 3 cytochrome c oxidase from Thermus thermophilus coupled to single electron injection into the O and O H states
AU - Siletsky, Sergey A.
AU - Belevich, Ilya
AU - Belevich, Nikolai P.
AU - Soulimane, Tewfik
AU - Wikström, Mårten
N1 - Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/11
Y1 - 2017/11
N2 - Two electrogenic phases with characteristic times of ~ 14 μs and ~ 290 μs are resolved in the kinetics of membrane potential generation coupled to single-electron reduction of the oxidized “relaxed” O state of ba 3 oxidase from T. thermophilus (O → E transition). The rapid phase reflects electron redistribution between Cu A and heme b. The slow phase includes electron redistribution from both Cu A and heme b to heme a 3 , and electrogenic proton transfer coupled to reduction of heme a 3 . The distance of proton translocation corresponds to uptake of a proton from the inner water phase into the binuclear center where heme a 3 is reduced, but there is no proton pumping and no reduction of Cu B . Single-electron reduction of the oxidized “unrelaxed” state (O H → E H transition) is accompanied by electrogenic reduction of the heme b/heme a 3 pair by Cu A in a “fast” phase (~ 22 μs) 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 a 3 pair to the Cu B 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 Cu B 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.
AB - Two electrogenic phases with characteristic times of ~ 14 μs and ~ 290 μs are resolved in the kinetics of membrane potential generation coupled to single-electron reduction of the oxidized “relaxed” O state of ba 3 oxidase from T. thermophilus (O → E transition). The rapid phase reflects electron redistribution between Cu A and heme b. The slow phase includes electron redistribution from both Cu A and heme b to heme a 3 , and electrogenic proton transfer coupled to reduction of heme a 3 . The distance of proton translocation corresponds to uptake of a proton from the inner water phase into the binuclear center where heme a 3 is reduced, but there is no proton pumping and no reduction of Cu B . Single-electron reduction of the oxidized “unrelaxed” state (O H → E H transition) is accompanied by electrogenic reduction of the heme b/heme a 3 pair by Cu A in a “fast” phase (~ 22 μs) 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 a 3 pair to the Cu B 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 Cu B 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.
KW - Catalytic cycle intermediates
KW - Charge transfer steps
KW - Cytochrome c oxidase
KW - Membrane potential
KW - Thermus thermophilus
UR - http://www.scopus.com/inward/record.url?scp=85028083496&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2017.08.007
DO - 10.1016/j.bbabio.2017.08.007
M3 - Article
C2 - 28807731
AN - SCOPUS:85028083496
SN - 0005-2728
VL - 1858
SP - 915
EP - 926
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 11
ER -