EPR study of electron transport in the cyanobacterium Synechocystis sp. PCC 6803: oxygen-dependent interrelations between photosynthetic and respiratory electron transport chains.
In this work, we investigated electron transport processes in the cyanobacterium Synechocystis sp. PCC 6803, with a special emphasis focused on oxygen-dependent interrelations between photosynthetic and respiratory electron transport chains. Redox transients of the photosystem I primary donor P700 and oxygen exchange processes were measured by the EPR method under the same experimental conditions. To discriminate between the factors controlling electron flow through photosynthetic and respiratory electron transport chains, we compared the P700 redox transients and oxygen exchange processes in wild type cells and mutants with impaired photosystem II and terminal oxidases (CtaI, CydAB, CtaDEII). It was shown that the rates of electron flow through both photosynthetic and respiratory electron transport chains strongly depended on the transmembrane proton gradient and oxygen concentration in cell suspension. Electron transport through photosystem I was controlled by two main mechanisms: (i) oxygen-dependent acceleration of electron transfer from photosystem I to NADP(+), and (ii) slowing down of electron flow between photosystem II and photosystem I governed by the intrathylakoid pH. Inhibitor analysis of P700 redox transients led us to the conclusion that electron fluxes from dehydrogenases and from cyclic electron transport pathway comprise 20-30% of the total electron flux from the intersystem electron transport chain to P700(+).
Trubitsin
Boris V
BV
Department of Biophysics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119992, Russia.
Ptushenko
Vasilii V
VV
Koksharova
Olga A
OA
Mamedov
Mahir D
MD
Vitukhnovskaya
Liya A
LA
Grigor'ev
Igor A
IA
Semenov
Alexey Yu
AY
Tikhonov
Alexander N
AN
D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D013113:Spin Labels; D046939:Synechocystis / Q000378:metabolism* / Q000502:physiology
D013113:Spin Labels; D010100:Oxygen