Recent Understanding on the Photosystem of Purple Photosynthetic Bacteria
Recent Understanding on the Photosystem of Purple Photosynthetic Bacteria
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DOI：
10.1007/978-3-319-25400-5_22
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发表时间：
2016
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影响因子：
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通讯作者：
Z. Wang-Otomo
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文献类型：
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作者：
Z. Wang-Otomo
细菌光合作用为研究光能获取和转化的基本机制提供了一个理想的简化模型系统。在这个过程中的早期事件是由两个不同的组成部分，光捕获（LH） 配合物和反应中心（RC） .紫色光合细菌的LH复合物主要分为两种类型：围绕RC的核心LH 1复合物和围绕LH 1存在的外围LH 2复合物。除了捕光，LH 1还在醌（Q）中发挥作用。 RC和细胞膜中醌库之间的转运。虽然已知RC和LH 2的几个高分辨率结构，但LH 1的结构仍处于低分辨率。本文报道了嗜热紫硫细菌Thermochromatiumtepidum的LH 1-RC复合物的晶体结构。该配合物的特征在于增强的热稳定性和在915 nm处的LH 1的最大吸收。这些特性已被证明是由Ca 2+离子调节。结构表明，LH 1络合物在RC周围呈封闭式排列，LH 1BChlamolecules形成部分重叠的环，其Mg-Mg间距比LH 2中B850的短.结构的证据是第一次提供了可能的泛醌途径在封闭的LH 1复合物。鉴定了Ca 2+结合位点。讨论了醌转运、Ca ~（2+）调节以及LH 1与RC相互作用的分子机制。
Bacterial photosynthesis provides a simplified model system ideally for studying the basic mechanism of light-energy harvest and conversion. The early events in this process are carried out by two distinct components, the light-harvesting (LH) complexes and the reaction center (RC) . The LH complexes in purple photosynthetic bacteria are classified into two major types, the core LH1 complex that surrounds the RC and the peripheral LH2 complex that exists around the LH1. In addition to light-harvesting, the LH1 also plays a role in quinone (Q) transport between the RC and quinone pool in the cell membrane. While several high-resolution structures are known for the RC and LH2, the structures of LH1 remained at low resolutions. Here, the crystal structure of a LH1-RC complex from thermophilic purple sulfur bacteriumThermochromatiumtepidumis described. This complex is characterized by an enhanced thermostability and an absorption maximum at 915 nm for the LH1. These properties have been shown to be regulated by Ca2+ions. The structure reveals a closed arrangement of LH1 complex around the RC, and the LH1 BChlamolecules form a partially overlapping ring with a shorter Mg–Mg spacing compared with that of B850 in LH2. Structural evidence is for the first time provided for the possible ubiquinone pathway in the closed LH1 complex. The Ca2+-binding sites are identified. Molecular mechanisms of quinone transport, Ca2+-regulation and interaction between LH1 and RC are discussed.