Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803

FEBS Letters

Vermaas, Wim F.J.¹  Styling, Stenbjörn¹  Shen, Gaozhong² 

[1] Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden;Department of Botany and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, AZ 85287-1601, USA

关键词: Thylakoid membrane;    Photosynthesis;    Electron transport;    Plastoquinone;    Respiration;    KCN-sensitive oxidase;    DCMU;    3-(3;    4-dichlorophenyl)-1;    1-dimethylurea;    DMBQ;    2;    6-dimethyl-p benzoquinone;    F o;    prompt fluorescence;    F v;    variable fluorescence;    HEPES;    4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid;    PS I;    photosystem I;    PS II;    photosystem II;    QA;    the first quinone-type electron acceptor in photosystem II;   

DOI  :  10.1016/0014-5793(94)80638-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The reduction and reoxidation kinetics of the first quinone-type electron acceptor in photosystem II, Q_A ⁻, were measured by fluorescence in a light-tolerant, photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, which shows excellent amplitudes of variable fluorescence, the rate of Q_A ⁻ oxidation after photoreduction of the plastoquinone pool was about half of that in the presence of photosystem I. However, upon addition of 5 mM KCN, Q_A ⁻ decay was very slow, and the rate was comparable to that seen in the presence of diuron, which blocks electron transport between Q_A and Q_B. The KCN-imposed block of Q_A ⁻ oxidation was removed efficiently by addition of exogenous quinones that can oxidize the plastoquinone pool. These results indicate that, in the absence of photosystem I, photosystem II-generated electrons are used very effectively by an oxidase located in the thylakoid; this oxidase may be a component of the respiratory chain.

【 授权许可】

Unknown