Azevedo Jacinthe, Courtois Florence, Hakimi Mohamed-Ali, Demarsy Emilie, Lagrange Thierry, Alcaraz Jean-Pierre, Jaiswal Pankaj, Maréchal-Drouard Laurence, Lerbs-Mache Silva
Laboratoire Plastes et Differénciation Cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, F-38041 Grenoble Cedex 9, France.
Proc Natl Acad Sci U S A. 2008 Jul 1;105(26):9123-8. doi: 10.1073/pnas.0800909105. Epub 2008 Jun 20.
The plastid genome of dicotyledonous plants is transcribed by three different RNA polymerases; an eubacterial-type enzyme, PEP; and two phage-type enzymes, RPOTp and RPOTmp. RPOTp plays an important role in chloroplast transcription, biogenesis, and mesophyll cell proliferation. RPOTmp fulfills a specific function in the transcription of the rrn operon in proplasts/amyloplasts during seed imbibition/germination and a more general function in chloroplasts during later developmental stages. In chloroplasts, RPOTmp is tightly associated with thylakoid membranes indicating that functional switching of RPOTmp is connected to thylakoid association. By using the yeast two-hybrid system, we have identified two proteins that interact with RPOTmp. The two proteins are very similar, both characterized by three N-terminal transmembrane domains and a C-terminal RING domain. We show that at least one of these proteins is an intrinsic thylakoid membrane protein that fixes RPOTmp on the stromal side of the thylakoid membrane, probably via the RING domain. A model is presented in which light by triggering the synthesis of the RING protein determines membrane association and functional switching of RPOTmp.
双子叶植物的质体基因组由三种不同的RNA聚合酶转录；一种真细菌型酶，即PEP；以及两种噬菌体型酶，RPOTp和RPOTmp。RPOTp在叶绿体转录、生物发生和叶肉细胞增殖中起重要作用。RPOTmp在种子吸胀/萌发期间原质体/造粉体中rrn操纵子的转录中发挥特定功能，在后期发育阶段的叶绿体中发挥更普遍的功能。在叶绿体中，RPOTmp与类囊体膜紧密相关，这表明RPOTmp的功能转换与类囊体关联有关。通过使用酵母双杂交系统，我们鉴定出了两种与RPOTmp相互作用的蛋白质。这两种蛋白质非常相似，都具有三个N端跨膜结构域和一个C端RING结构域。我们表明，这些蛋白质中至少有一种是内在类囊体膜蛋白，它可能通过RING结构域将RPOTmp固定在类囊体膜的基质侧。本文提出了一个模型，其中光通过触发RING蛋白的合成来决定RPOTmp的膜关联和功能转换。
