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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Atomic-level structural and functional model of a bacterial photosynthetic membrane vesicle
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Atomic-level structural and functional model of a bacterial photosynthetic membrane vesicle

机译：细菌光合膜囊泡的原子级结构和功能模型

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摘要

The photosynthetic unit (PSU) of purple photosynthetic bacteria consists of a network of bacteriochlorophyll-protein complexes that absorb solar energy for eventual conversion to ATP. Because of its remarkable simplicity, the PSU can serve as a prototype for studies of cellular organelles. In the purple bacterium Rhodobacter sphaeroides the PSU forms spherical invaginations of the inner membrane, ≈70 nm in diameter, composed mostly of light-harvesting complexes, LH1 and LH2, and reaction centers (RCs). Atomic force microscopy studies of the intracytoplasmic membrane have revealed the overall spatial organization of the PSU. In the present study these atomic force microscopy data were used to construct three-dimensional models of an entire membrane vesicle at the atomic level by using the known structure of the LH2 complex and a structural model of the dimeric RC-LH1 complex. Two models depict vesicles consisting of 9 or 18 dimeric RC-LH1 complexes and 144 or 101 LH2 complexes, representing a total of 3,879 or 4,464 bacteriochlorophylls, respectively. The in silico reconstructions permit a detailed description of light absorption and electronic excitation migration, including computation of a 50-ps excitation lifetime and a 95% quantum efficiency for one of the model membranes, and demonstration of excitation sharing within the closely packed RC-LH1 dimer arrays.
机译：紫色光合作用细菌的光合作用单元（PSU）由细菌叶绿素-蛋白质复合物网络组成，该网络吸收太阳能以最终转化为ATP。由于其卓越的简便性，PSU可以作为研究细胞器的原型。在紫色细菌球形红细菌（Rhodobacter sphaeroides）中，PSU形成内膜的球形内陷，直径约70 nm，主要由捕光性复合物LH1和LH2以及反应中心（RCs）组成。细胞质膜的原子力显微镜研究揭示了PSU的整体空间组织。在本研究中，这些原子力显微镜数据通过使用LH2配合物的已知结构和二聚RC-LH1配合物的结构模型，在原子水平上构建了整个膜囊泡的三维模型。两种模型描绘了由9个或18个二聚体RC-LH1复合体和144个或101个LH2复合体组成的囊泡，分别代表总共3,879个或4,464个细菌叶绿素。计算机模拟重建可以详细描述光吸收和电子激发迁移，包括计算其中一种模型膜的50ps激发寿命和95％量子效率，并演示了紧密包装的RC-LH1中的激发共享二聚体阵列。

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