Redox-state dependent blinking of single photosystem I trimers at around liquid-nitrogen temperature
Redox-state dependent blinking of single photosystem I trimers at around liquid-nitrogen temperature
复制标题
液氮温度附近单光系统 I 三聚体的氧化还原态依赖性闪烁
DOI：
10.1016/j.bbabio.2018.11.002
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
--
作者：
Jana;S.;Du;T.;Nagao;R.;Noguchi;T.;Shibata;Y.
光合天线系统中的有效光收集受到天线色素响应蛋白质构象动力学的参差不齐且波动的能量景观的干扰。这种情况在含有红移叶绿素（红色 Chls）且激发能远低于主要供体的光系统 I（PSI）中尤其明显。本研究旨在阐明从集胞藻中分离的 PSI 的光捕获动态。 PCC6803 在液氮温度下使用单分子光谱。在 80-100K 下监测单个 PSI 三聚体中红色 Chls 约 720nm 处的荧光发射，经常观察到发射强度的间歇性变化，即所谓的闪烁。它的时间尺度只有几十秒。闪烁幅度取决于叶绿醌 (A1) 的氧化还原状态。根据X射线晶体结构计算了A1上的负电荷引起的Chls的电致变色位移。发现结合在 A1 附近的 Chl 分子 Chl-A839（根据 PDB 5OY0 编号）具有较大的电致变色位移。该叶绿素与邻近叶绿素 (A838) 具有强激子耦合，预计其位点能量由与精氨酸残基 (ArgF84) 的相互作用决定 [Adolphs et al., 2010]。提出了眨眼的可能情况。 ArgF84 的构象波动影响 Chl-A838 的激发能，这扰乱了红色 Chl 和作为猝灭剂的 P700 的阳离子形式之间激发能的分支比。 Chl-A839 的电致变色位移增强了 ArgF84 构象动力学的效果。
Efficient light harvesting in a photosynthetic antenna system is disturbed by a ragged and fluctuating energy landscape of the antenna pigments in response to the conformation dynamics of the protein. This situation is especially pronounced in Photosystem I (PSI) containing red shifted chlorophylls (red Chls) with the excitation energy much lower than the primary donor. The present study was conducted to clarify light-harvesting dynamics of PSI isolated fromSynechocystissp. PCC6803 by using single-molecule spectroscopy at liquid‑nitrogen temperatures. Fluorescence emission at around 720 nm from the red Chls in single PSI trimers was monitored at 80–100 K. Intermittent variations in the emission intensities, so-called blinking, were frequently observed. Its time scale lay in several tens of seconds. The blinking amplitude depended on the redox state of the phylloquinone (A1). Electrochromic shifts of Chls induced by the negative charge on A1were calculated based on the X-ray crystallographic structure. A Chl molecule, Chl-A839 (numbering according to PDB 5OY0), bound near A1was found to have a large electrochromic shift. This Chl has strong exciton coupling with neighboring Chl (A838) whose site energy was predicted to be determined by interaction with an arginine residue (ArgF84) [Adolphs et al., 2010]. A possible scenario of the blinking was proposed. Conformational fluctuations of ArgF84 seesaw the excitation-energy of Chl-A838, which perturbs the branching ratio of excitation-energy between the red Chl and the cationic form of P700 as a quencher. The electrochromic shift of Chl-A839 enhances the effect of the conformation dynamics of ArgF84.