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首页> 外文会议>International Congress of Photosynthesis >PROBING THE ACTIVE ELECTRON TRANSFER BRANCH IN THE PHOTOSYSTEM I REACTION CENTER FROM SYNECHOCYSTIS SP. PCC 6803
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PROBING THE ACTIVE ELECTRON TRANSFER BRANCH IN THE PHOTOSYSTEM I REACTION CENTER FROM SYNECHOCYSTIS SP. PCC 6803

机译：从SyneChocystis SP探测照相中的电力系统中的活性电子转移分支。 PCC 6803.

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Photosystem I (PS I) is a pigment-protein complex embedded in the thylakoid membrane that uses the energy of light to reduce ferredox-in or flavodoxin in cyanobacteria, algae and higher plants (Brettel 1997). According to the 2.5 A crystal structure,the electron transfer chain in PS I is comprised of six chlorophyll (Chl) molecules, two phylloquinones and three [4Fe-4S] clusters (Jordan et al 2001). The Chls and the phylloquinones are arranged in two pseudo-symmetric branches with ligands provided by the PsaA and PsaB protein sub-units. The presence of two highly symmetrical branches in the reaction center (RC) raises the question of which branch is active in electron transfer. In this work, point mutations were introduced near the primary electronacceptor sites assigned to A_0 in both the PsaA and PsaB branches of RC in the cyanobacterium Synechocystis sp. PCC 6803. The residues Met688_(PsaA) and Met668_(PsaB), which provide the axial ligands to the Mg~(2+) of the eC-A3 and eC-B3 Chls, were changed to leucine and asparagine (Chl notation follows Jordan et al 2001). The removal of the ligand is expected to alter the midpoint potential of the A_0/A_0~- redox pair and affect the kinetics of charge separation. In this work, we studied the dynamicsof primary charge separation and secondary electron transfer in these mutants by ultrafast optical pump-probe spectroscopy. Our results suggest that electron transfer in cyanobacterial PS I is asymmetric and occurs primarily along the PsaA branch of cofactors.
机译：光照I（PS I）是一种颜料蛋白质复合物，其嵌入着囊体膜中，使用光的能量来减少蓝藻，藻类和高等植物中的福兰多毒素或黄酮毒素（Brettel 1997）。根据2.5晶体结构，PS I中的电子转移链由六个叶绿素（CHL）分子，两个植物醌和三[4FE-4S]簇组成（Jordan等，2001）。 CHL和Phylloquinnes布置在两个伪对称分支中，配有由PSAA和PSAB蛋白质子单元提供的配体。反应中心（RC）中存在两个高度对称分支的分支提高了该分支在电子转移中活性的问题。在这项工作中，在Cyanobacterium snechocystis Sp中的rc的PSAA和PSAB分支中分配给A_0的主电接受位点附近引入点突变。 PCC 6803的残基Met688_（PSAA）和Met668_（PSAB），其提供了轴向配体的EC-A3和EC-B3的Chls中的Mg〜（2+），改变为亮氨酸和天冬酰胺（叶绿素​​符号如下约旦等人2001）。预期配体的除去将改变A_0 / A_0〜 - 氧化还原对的中点电位，并影响电荷分离的动力学。在这项工作中，我们通过超氮光学泵探针光谱研究了这些突变体中主要电荷分离和二次电子转移的动态。我们的研究结果表明，Cyanobacterial PS I中的电子转移是不对称的，并且主要沿辅助弧菌的PSAA分支发生。

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