Bína David, Gardian Zdenko, Herbstová Miroslava, Litvín Radek
Institute of Plant Molecular Biology, Biology Centre CAS, Branišovská 31, 370 05, České Budějovice, Czech Republic.
Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic.
Photosynth Res. 2017 Mar;131(3):255-266. doi: 10.1007/s11120-016-0315-1. Epub 2016 Oct 12.
Photosystem I (PSI) is a multi-subunit integral pigment-protein complex that performs light-driven electron transfer from plastocyanin to ferredoxin in the thylakoid membrane of oxygenic photoautotrophs. In order to achieve the optimal photosynthetic performance under ambient irradiance, the absorption cross section of PSI is extended by means of peripheral antenna complexes. In eukaryotes, this role is played mostly by the pigment-protein complexes of the LHC family. The structure of the PSI-antenna supercomplexes has been relatively well understood in organisms harboring the primary plastid: red algae, green algae and plants. The secondary endosymbiotic algae, despite their major ecological importance, have so far received less attention. Here we report a detailed structural analysis of the antenna-PSI association in the stramenopile alga Nannochloropsis oceanica (Eustigmatophyceae). Several types of PSI-antenna assemblies are identified allowing for identification of antenna docking sites on the PSI core. Instances of departure of the stramenopile system from the red algal model of PSI-Lhcr structure are recorded, and evolutionary implications of these observations are discussed.
光系统I（PSI）是一种多亚基整合色素蛋白复合体，在光合自养生物的类囊体膜中进行从质体蓝素到铁氧化还原蛋白的光驱动电子转移。为了在环境光照强度下实现最佳光合性能，PSI的吸收截面通过外周天线复合体得以扩展。在真核生物中，这一作用主要由LHC家族的色素蛋白复合体发挥。在具有原始质体的生物（红藻、绿藻和植物）中，PSI-天线超复合体的结构已得到相对较好的理解。次生内共生藻类尽管具有重要的生态学意义，但迄今为止受到的关注较少。在此，我们报告了对硅藻门的海洋微拟球藻（真眼点藻纲）中天线-PSI关联的详细结构分析。我们鉴定出了几种类型的PSI-天线组装体，从而得以确定天线在PSI核心上的对接位点。记录了硅藻门系统与红藻PSI-Lhcr结构模型的差异，并讨论了这些观察结果的进化意义。
