Electrogenic reduction of the primary electron donor P700 by plastocyanin in photosystem I complexes

FEBS Letters

Mamedov, Mahir D.¹  Mamedova, Aygun A.¹  Chamorovsky, Sergey K.²  Semenov, Alexey Yu.¹ 

[1] Department of Photobiochemistry, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119899 Moscow, Russia;Department of Biophysics, School of Biology, Moscow State University, 119899 Moscow, Russia

关键词: Photosystem I;    Plastocyanin;    Electron transfer;    Proteoliposome;    Electrogenic phase;    Flash-induced kinetics;    Synechocystis sp. PCC 6803;    Pc;    plastocyanin;    PS I;    photosystem I;    cyt;    cytochrome;    P700;    chlorophyll dimer;    FX;    FA;    FB;    4Fe–4S clusters;    A0;    monomeric chlorophyll;    A1;    phylloquinone;    RC;    reaction center;    Δψ;    transmembrane electric potential difference;   

DOI  :  10.1016/S0014-5793(01)02615-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

An electrometric technique was used to investigate electron transfer between spinach plastocyanin (Pc) and photooxidized primary electron donor P700 in photosystem I (PS I) complexes from the cyanobacterium Synechocystis sp. PCC 6803. In the presence of Pc, the fast unresolvable kinetic phase of membrane potential generation related to electron transfer between P700 and the terminal iron–sulfur acceptor F_B was followed by additional electrogenic phases in the microsecond and millisecond time scales, which contribute approximately 20% to the overall electrogenicity. These phases are attributed to the vectorial electron transfer from Pc to the protein-embedded chlorophyll dimer P700⁺ within the PsaA/PsaB heterodimer. The observed rate constant of the millisecond kinetic phase exhibited a saturation profile at increasing Pc concentration, suggesting the formation of a transient complex between Pc and PS I with the dissociation constant K _d of about 80 μM. A small but detectable fast electrogenic phase was observed at high Pc concentration. The rate constant of this phase was independent of Pc concentration, indicating that it is related to a first-order process.

【 授权许可】

Unknown