Spectroscopic characterization of PS I core complexes from thermophilic Synechococcus sp

FEBS Letters

Jekow, Petra²  Fromme, Petra¹  Schlodder, Eberhard¹  Lüneberg, Jürgen¹ 

[1] Max-Volmer-Institut für Biophysikalische und Physikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany;Institut für Kristallographie, Freie Universität Berlin, Takustr. 6, 14195 Berlin, Germany

关键词: Photosystem I;    Core protein;    Iron sulfur center;    Electron transfer;    Absorption difference spectroscopy;    BV;    benzylviologen;    CAPS;    (3-(Cyclohexylamino)-1-propane sulfonic acid;    Chl;    chlorophyll a;    d;    optical path for the measuring light;    DPIP;    2;    6-dichlorophenolindophenol;    DTT;    dithiothreitol;    FeS;    iron-sulfur-cluster;    MES;    2-(N-morpholino)-ethane sulfonic acid;    PS;    photosystem;    PS I core complex;    PS I without the extrinsic subunits C;    D and E;    SDS-PAGE;    sodium dodecyl sulfate polyacrylamide gel electrophoresis;   

DOI  :  10.1016/0014-5793(94)80364-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Monomeric and trimeric PS I complexes missing the three stromal subunits E,C and D (termed PS I core complexes) were prepared from the thermophilic cyanobacterium Synechococcus sp. by incubation with urea. The subunits E,C and D are sequentially removed. In the monomeric PS I the subunit C is removed with a half life of approx. 5 min. This is about eight times faster than in the trimeric PS I complex. In parallel with the removal of the F_AB containing subunit C the reduction kinetics of P700⁺ changed from a half life of about 25 ms to about 750 μs. The partner of P700⁺ in the 750 μs charge recombination was identified to be F_X by the difference spectrum of this phase. There are some minor differences in the spectra of trimeric and monomeric PS I core complexes. At 77K the forward electron transfer from A ⁻ ₁ to F_X is blocked in the major fraction of the PS I core complexes and P700⁺A⁻ ₁ recombines with a half life of about 220 μs. In the remaining fraction P700⁺F_X ⁻ is formed and decays with a half life of approx. 10 ms at 77 K. The kinetics of the forward electron transfer from A⁻ ₁ to the iron-sulfur-clusters was measured in the native PS I and the corresponding core complexes. The reoxidation kinetics of A⁻ ₁ are identical in both cases (t ₁₂ = 180 ns). We conclude that Fx is an obligatory intermediate in the normal forward electron transfer.

【 授权许可】

Unknown