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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR
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Structure of the light-harvesting bacteriochlorophyll c assembly in chlorosomes from Chlorobium limicola determined by solid-state NMR

机译：固态NMR测定绿假单胞菌质体中的捕光细菌叶绿素c组装结构。

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摘要

We have determined the atomic structure of the bacteriochlorophyll c (BChl c) assembly in a huge light-harvesting organelle, the chlorosome of green photosynthetic bacteria, by solid-state NMR. Previous electron microscopic and spectroscopic studies indicated that chlorosomes have a cylindrical architecture with a diameter of approximate to 10 nm consisting of layered BChl molecules. Assembly structures in huge noncrystalline chlorosomes have been proposed based mainly on structure-dependent chemical shifts and a few distances acquired by solid-state NMR, but those studies did not provide a definite structure. Our approach is based on C-13 dipolar spin-diffusion solid-state NMR of uniformly C-13-labeled chlorosomes under magic-angle spinning. Approximately 90 intermolecular C-C distances were obtained by simultaneous assignment of distance correlations and structure optimization preceded by polarization-transfer matrix analysis. it was determined from the approximate to 90 intermolecular distances that BChl c molecules form piggyback-dimer-based parallel layers. This finding rules out the well known monomer-based structures. A molecular model of the cylinder in the chlorosome was built by using this structure. It provided insights into the mechanisms of efficient light harvesting and excitation transfer to the reaction centers. This work constitutes an important advance in the structure determination of huge intact systems that cannot be crystallized.
机译：我们已经通过固态NMR确定了一个巨大的光收集细胞器中的细菌叶绿素c（BChl c）组件的原子结构，即绿色光合细菌的氯体。先前的电子显微镜和光谱研究表明，脂质体具有圆柱形结构，其直径约为10 nm，由层状BChl分子组成。有人提出了巨大的非晶态核小体中的组装结构，主要是基于结构相关的化学位移和固态NMR获得的一些距离，但这些研究并未提供确定的结构。我们的方法是基于在魔角旋转条件下均匀地C-13标记的脂质体的C-13偶极自旋扩散固态NMR。通过同时分配距离相关性和结构优化，然后进行极化转移矩阵分析，可获得大约90个分子间C-C距离。从大约90个分子间距离可以确定BChl c分子形成了基于背back二聚体的平行层。该发现排除了众所周知的基于单体的结构。通过使用这种结构，建立了氯仿中圆柱体的分子模型。它提供了有效的光收集和激发转移到反应中心的机制的见解。这项工作构成了无法结晶的完整系统的结构确定方面的重要进展。

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