Center for Insoluble Protein Structures, Interdisciplinary Nanoscience Center, Aarhus University, Langelandsgade 140, Arhus C, Aarhus, Denmark.
Photosynth Res. 2010 Jun;104(2-3):233-43. doi: 10.1007/s11120-009-9519-y. Epub 2010 Jan 14.
In contrast to photosynthetic reaction centers, which share the same structural architecture, more variety is found in the light-harvesting antenna systems of phototrophic organisms. The largest antenna system described, so far, is the chlorosome found in anoxygenic green bacteria, as well as in a recently discovered aerobic phototroph. Chlorosomes are the only antenna system, in which the major light-harvesting pigments are organized in self-assembled supramolecular aggregates rather than on protein scaffolds. This unique feature is believed to explain why some green bacteria are able to carry out photosynthesis at very low light intensities. Encasing the chlorosome pigments is a protein-lipid monolayer including an additional antenna complex: the baseplate, a two-dimensional paracrystalline structure containing the chlorosome protein CsmA and bacteriochlorophyll a (BChl a). In this article, we review current knowledge of the baseplate antenna complex, which physically and functionally connects the chlorosome pigments to the reaction centers via the Fenna-Matthews-Olson protein, with special emphasis on the well-studied green sulfur bacterium Chlorobaculum tepidum (previously Chlorobium tepidum). A possible role for the baseplate in the biogenesis of chlorosomes is discussed. In the final part, we present a structural model of the baseplate through combination of a recent NMR structure of CsmA and simulation of circular dichroism and optical spectra for the CsmA-BChl a complex.
与共享相同结构架构的光合反应中心不同，在光养生物的光捕获天线系统中发现了更多的多样性。迄今为止，描述的最大天线系统是在厌氧绿菌以及最近发现的好氧光养生物中发现的叶绿素体。叶绿素体是唯一的天线系统，其中主要的光捕获色素组织在自组装超分子聚集体中，而不是在蛋白质支架上。人们认为这种独特的特征可以解释为什么一些绿菌能够在非常低的光强度下进行光合作用。包裹叶绿素体色素的是一个蛋白质-脂质单层，其中包括一个附加的天线复合物：基板，这是一个二维准晶结构，包含叶绿素体蛋白 CsmA 和细菌叶绿素 a（BChl a）。在本文中，我们回顾了基板天线复合物的当前知识，该复合物通过 Fenna-Matthews-Olson 蛋白将叶绿素体色素与反应中心在物理和功能上连接起来，特别强调了研究得很好的绿硫细菌 Chlorobaculum tepidum（以前称为 Chlorobium tepidum）。讨论了基板在叶绿素体生物发生中的可能作用。在最后一部分，我们通过最近的 CsmA NMR 结构和 CsmA-BChl a 复合物的圆二色性和光光谱模拟组合，呈现了基板的结构模型。
