被称为“光系统-I”的蛋白超级复合物在聚集能量方面是一个“明星”：它是自然界最高效的光—化学机器，它所吸收的几乎每个光子都被用来驱动电子的传输；而且作为植物、绿藻和藻青菌中普遍存在的光聚集器官，它为地球上几乎所有高等生物提供能量。现在，植物“光系统-I”的X-射线晶体结构已经以3.4?魡的分辨率被确定，从而显示了这种超高效率背后所存在的高度复杂性。从豌豆植物中分离出来的该复合物包含17个蛋白亚单元、168个叶绿素分子、2个叶绿醌分子、3个Fe4S4簇和5个类胡萝卜素分子。
英文原文：
Nature 447, 58-63 (3 May 2007) | doi:10.1038/nature05687; Received 1 December 2006; Accepted 19 February 2007
The structure of a plant photosystem I supercomplex at 3.4 Å resolution
Alexey Amunts1, Omri Drory1 & Nathan Nelson1
Department of Biochemistry, The George S. Wise Faculty of Life Sciences, The Daniella Rich Institute for Structural Biology, Tel Aviv University, Tel Aviv, 69978, Israel
Correspondence to: Nathan Nelson1 Correspondence and requests for materials should be addressed to N.N. (Email: nelson@post.tau.ac.il).
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Abstract
All higher organisms on Earth receive energy directly or indirectly from oxygenic photosynthesis performed by plants, green algae and cyanobacteria. Photosystem I (PSI) is a supercomplex of a reaction centre and light-harvesting complexes. It generates the most negative redox potential in nature, and thus largely determines the global amount of enthalpy in living systems. We report the structure of plant PSI at 3.4 Å resolution, revealing 17 protein subunits. PsaN was identified in the luminal side of the supercomplex, and most of the amino acids in the reaction centre were traced. The crystal structure of PSI provides a picture at near atomic detail of 11 out of 12 protein subunits of the reaction centre. At this level, 168 chlorophylls (65 assigned with orientations for Qx and Qy transition dipole moments), 2 phylloquinones, 3 Fe4S4 clusters and 5 carotenoids are described. This structural information extends the understanding of the most efficient nano-photochemical machine in nature.
