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Atomic Force Microscopy Studies of Native Photosynthetic Membranes

机译：天然光合膜的原子力显微镜研究

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ABSTRACT: In addition to providing the earliest surface images of a native photosynthetic membrane atnsubmolecular resolution, examination of the intracytoplasmic membrane (ICM) of purple bacteria by atomicnforce microscopy (AFM) has revealed a wide diversity of species-dependent arrangements of closely packednlight-harvesting (LH) antennae, capable of fulfilling the basic requirements for efficient collection, transmission,nand trapping of radiant energy. A highly organized architecture was observed with fused preparations of thenpseudocrystalline ICM of Blastochloris Viridis, consiting of hexagonally packed monomeric reaction centernlight-harvesting 1 (RC-LH1) core complexes. Among strains which also form a peripheral LH2 antenna, imagesnof ICM patches from Rhodobacter sphaeroides exhibited well-ordered, interconnected networks of dimericnRC-LH1 core complexes intercalated by rows of LH2, coexisting with LH2-only domains. Other peripheralnantenna-containing species, notably Rhodospirillum photometricum and Rhodopseudomonas palustris, showedna less regular organization, with mixed regions of LH2 and RC-LH1 cores, intermingled with large,nparacrystalline domains. The ATP synthase and cytochrome bc1 complex were not observed in any of thesentopographs and are thought to be localized in the adjacent cytoplasmic membrane or in inaccessible ICMnregions separated from the flat regions imaged by AFM. The AFM images have served as a basis for atomicresolutionnmodeling of the ICM vesicle surface, as well as forces driving segregation of photosynthetic complexesninto distinct domains. Docking of atomic-resolution molecular structures into AFM topographs of Rsp.nphotometricum membranes generated precise in situ structural models of the core complex surrounded bynLH2 rings and a region of tightly packed LH2 complexes. A similar approach has generated a model of thenhighly curved LH2-only membranes of Rba. sphaeroides which predicts that sufficient space exists betweennLH2 complexes for quinones to diffuse freely. Measurement of the intercomplex distances between adjacentnLH2 rings of Phaeospirillum molischianum has permitted the first calculation of the separation ofnbacteriochlorophyll a molecules in the native ICM. A recent AFM analysis of the organization of green plantnphotosystem II (PSII) in grana thylakoids revealed the protruding oxygen-evolving complex, crowded togethernin parallel alignment at three distinct levels of stacked membranes over the lumenal surface. The results alsonconfirmed that PSII-LHCII supercomplexes are displaced relative to one another in opposing grana membranes.
机译：摘要：除了提供亚分子分辨率的天然光合膜的最早表面图像外，通过原子力显微镜（AFM）对紫色细菌的胞质内膜（ICM）进行的检查还发现，种类繁多的物种紧密排列的捕光性安排多种多样（LH）天线，能够满足有效收集，传输，捕获和捕获辐射能的基本要求。观察到了高度组织化的体系结构，其融合了拟绿假单胞菌的假晶体ICM，包括六边形堆积的单体反应中心-捕光1（RC-LH1）核心复合物。在也形成外围LH2天线的菌株中，来自球形球形红细菌的ICM贴片的图像显示出排列整齐的，相互连接的二聚体RC-LH1核心复合物网络，其中插入的LH2行与LH2仅域共存。其他含周边天线的物种，尤其是光度螺旋藻和光生红假单胞菌，则显示出较不规则的组织，具有混合的LH2和RC-LH1核心区域，并混有较大的正晶域。 ATP合酶和细胞色素bc1复合物未在任何透射描记仪中观察到，并被认为位于邻近的细胞质膜或与AFM成像的平坦区域分开的难以接近的ICMn区域中。 AFM图像已成为ICM囊泡表面的原子分辨率建模的基础，以及将光合复合物驱动分离到不同域的作用力。将原子分辨率分子结构对接到Rsp.nphotometricum膜的AFM地形图中，可以生成由nLH2环和紧密堆积的LH2配合物区域包围的核心配合物的精确原位结构模型。一种类似的方法已经生成了Rba仅高度弯曲的仅LH2的膜的模型。可以预测nLH2配合物之间存在足够的空间，使醌自由扩散。通过测量相邻的Phaeospirillum molischianum的nLH2环之间的复杂距离，可以对天然ICM中的细菌叶绿素a分子的分离进行首次计算。最近的AFM分析显示，类植物类囊体中绿色植物光系统II（PSII）的组织结构揭示了突出的放氧复合物，在腔表面上三个不同的堆叠膜水平上以平行排列的方式聚集在一起。该结果也证实了PSII-LHCII超复合物在相对的格兰膜中相对于彼此移位。

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  • 来源
    《Biochemistry》 |2009年第17期|p.3679-3698|共20页
  • 作者

    James N. Sturgis Jaimey D. Tucker John D. Olsen C. Neil Hunter and Robert A. Niederman;

  • 作者单位

    Laboratoire d’Inge´nierie des Syste`mes Macromole´culaires, UPR 9027, Aix Marseille UniVersite´, 31 Chemin Joseph Aiguier,13402 Marseilles, France, Department of Molecular Biology and Biotechnology, UniVersity of Sheffield, Sheffield S10 2TN, U.K., andDepartment of Molecular Biology and Biochemistry, Rutgers UniVersity, Piscataway, New Jersey 08854-8082;

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