Roose Johnna L, Frankel Laurie K, Bricker Terry M
From the Department of Biological Sciences, Biochemistry and Molecular Biology Section, Louisiana State University, Baton Rouge, Louisiana 70803.
From the Department of Biological Sciences, Biochemistry and Molecular Biology Section, Louisiana State University, Baton Rouge, Louisiana 70803
J Biol Chem. 2014 Aug 22;289(34):23776-85. doi: 10.1074/jbc.M114.589085. Epub 2014 Jul 9.
Photosystem I (PS I) is a multisubunit membrane protein complex that functions as a light-driven plastocyanin-ferredoxin oxidoreductase. The PsbP domain protein 1 (PPD1; At4g15510) is located in the thylakoid lumen of plant chloroplasts and is essential for photoautotrophy, functioning as a PS I assembly factor. In this work, RNAi was used to suppress PPD1 expression, yielding mutants displaying a range of phenotypes with respect to PS I accumulation and function. These PPD1 RNAi mutants showed a loss of assembled PS I that was correlated with loss of the PPD1 protein. In the most severely affected PPD1 RNAi lines, the accumulated PS I complexes exhibited defects in electron transfer from plastocyanin to the oxidized reaction center P700 (+). The defects in PS I assembly in the PPD1 RNAi mutants also had secondary effects with respect to the association of light-harvesting antenna complexes to PS I. Because of the imbalance in photosystem function in the PPD1 RNAi mutants, light-harvesting complex II associated with and acted as an antenna for the PS I complexes. These results provide new evidence for the role of PPD1 in PS I biogenesis, particularly as a factor essential for proper assembly of the lumenal portion of the complex.
光系统I（PS I）是一种多亚基膜蛋白复合体，作为光驱动的质体蓝素-铁氧化还原蛋白氧化还原酶发挥作用。PsbP结构域蛋白1（PPD1；At4g15510）位于植物叶绿体的类囊体腔中，是光合自养所必需的，作为PS I组装因子发挥作用。在这项工作中，使用RNA干扰来抑制PPD1的表达，产生了一系列在PS I积累和功能方面表现出不同表型的突变体。这些PPD1 RNA干扰突变体显示组装好的PS I缺失，这与PPD1蛋白的缺失相关。在受影响最严重的PPD1 RNA干扰株系中，积累的PS I复合体在从质体蓝素到氧化反应中心P700（+）的电子传递方面表现出缺陷。PPD1 RNA干扰突变体中PS I组装的缺陷对于捕光天线复合体与PS I的结合也有次级效应。由于PPD1 RNA干扰突变体中光系统功能的失衡，捕光复合体II与PS I复合体结合并作为其天线发挥作用。这些结果为PPD1在PS I生物发生中的作用提供了新的证据，特别是作为复合体腔部分正确组装所必需的一个因子。
