Wegener Kimberly M, Welsh Eric A, Thornton Leeann E, Keren Nir, Jacobs Jon M, Hixson Kim K, Monroe Matthew E, Camp David G, Smith Richard D, Pakrasi Himadri B
Department of Biology, Washington University, St. Louis, Missouri 63130.
Environmental Molecular Sciences Biological Sciences Division and Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352.
J Biol Chem. 2008 Oct 10;283(41):27829-27837. doi: 10.1074/jbc.M803918200. Epub 2008 Aug 8.
Photosystem II (PSII) is a large membrane protein complex that performs the water oxidation reactions of photosynthesis in cyanobacteria, algae, and plants. The unusual redox reactions in PSII often lead to damage, degradation, and reassembly of this molecular machine. To identify novel assembly factors, high sensitivity proteomic analysis of PSII purified from the cyanobacterium Synechocystis sp. PCC 6803 was performed. This analysis identified six PSII-associated proteins that are encoded by an operon containing nine genes, slr0144 to slr0152. This operon encodes proteins that are not essential components of the PSII holocomplex but accumulate to high levels in pre-complexes lacking any of the lumenal proteins PsbP, PsbQ, or PsbV. The operon contains genes with putative binding domains for chlorophylls and bilins, suggesting these proteins may function as a reservoir for cofactors needed during the PSII lifecycle. Genetic deletion of this operon shows that removal of these protein products does not alter photoautotrophic growth or PSII fluorescence properties. However, the deletion does result in decreased PSII-mediated oxygen evolution and an altered distribution of the S states of the catalytic manganese cluster. These data demonstrate that the proteins encoded by the genes in this operon are necessary for optimal function of PSII and function as accessory proteins during assembly of the PSII complex. Thus, we have named the products of the slr0144-slr0152 operon Pap (Photosystem II assembly proteins).
光系统II（PSII）是一种大型膜蛋白复合物，在蓝细菌、藻类和植物中进行光合作用的水氧化反应。PSII中异常的氧化还原反应常常导致这个分子机器的损伤、降解和重新组装。为了鉴定新的组装因子，对从集胞藻属PCC 6803蓝细菌中纯化的PSII进行了高灵敏度蛋白质组学分析。该分析鉴定出六种与PSII相关的蛋白质，它们由一个包含九个基因（slr0144至slr0152）的操纵子编码。该操纵子编码的蛋白质不是PSII全复合物的必需成分，但在缺乏任何腔蛋白PsbP、PsbQ或PsbV的预复合物中大量积累。该操纵子包含具有叶绿素和胆色素假定结合结构域的基因，表明这些蛋白质可能作为PSII生命周期中所需辅因子的储存库。对该操纵子进行基因缺失表明，去除这些蛋白质产物不会改变光合自养生长或PSII荧光特性。然而，缺失确实导致PSII介导的氧释放减少以及催化锰簇S态的分布改变。这些数据表明，该操纵子中的基因编码的蛋白质是PSII最佳功能所必需的，并且在PSII复合物组装过程中作为辅助蛋白发挥作用。因此，我们将slr0144 - slr0152操纵子的产物命名为Pap（光系统II组装蛋白）。
