Knoppová Jana, Yu Jianfeng, Konik Peter, Nixon Peter J, Komenda Josef
Institute of Microbiology, Center Algatech, Opatovický mlýn, 37981 Třeboň, Czech Republic Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05 České Budějovice, Czech Republic.
Department of Life Sciences, Sir Ernst Chain Building-Wolfson Laboratories, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
Plant Cell Physiol. 2016 Sep;57(9):1921-31. doi: 10.1093/pcp/pcw115. Epub 2016 Jul 7.
Although the PSII complex is highly conserved in cyanobacteria and chloroplasts, the PsbU and PsbV subunits stabilizing the oxygen-evolving Mn4CaO5 cluster in cyanobacteria are absent in chloroplasts and have been replaced by the PsbP and PsbQ subunits. There is, however, a distant cyanobacterial homolog of PsbP, termed CyanoP, of unknown function. Here we show that CyanoP plays a role in the early stages of PSII biogenesis in Synechocystis sp. PCC 6803. CyanoP is present in the PSII reaction center assembly complex (RCII) lacking both the CP47 and CP43 modules and binds to the smaller D2 module. A small amount of larger PSII core complexes co-purifying with FLAG-tagged CyanoP indicates that CyanoP can accompany PSII on most of its assembly pathway. A role in biogenesis is supported by the accumulation of unassembled D1 precursor and impaired formation of RCII in a mutant lacking CyanoP. Interestingly, the pull-down preparations of CyanoP-FLAG from a strain lacking CP47 also contained PsbO, indicating engagement of this protein with PSII at a much earlier stage in assembly than previously assumed.
尽管光系统II（PSII）复合物在蓝细菌和叶绿体中高度保守，但在叶绿体中不存在稳定蓝细菌中放氧的Mn4CaO5簇的PsbU和PsbV亚基，它们已被PsbP和PsbQ亚基取代。然而，存在一种功能未知的PsbP的远缘蓝细菌同源物，称为CyanoP。在这里，我们表明CyanoP在集胞藻PCC 6803的PSII生物发生早期阶段发挥作用。CyanoP存在于缺乏CP47和CP43模块的PSII反应中心组装复合物（RCII）中，并与较小的D2模块结合。与带有FLAG标签的CyanoP共纯化的少量较大的PSII核心复合物表明，CyanoP可以在其大部分组装途径中伴随PSII。在缺乏CyanoP的突变体中，未组装的D1前体的积累和RCII形成受损支持了其在生物发生中的作用。有趣的是，从缺乏CP47的菌株中拉下的CyanoP-FLAG制剂中也含有PsbO，这表明该蛋白在组装过程中比以前认为的更早阶段就与PSII结合。
