Disassembly and Degradation of Photosystem I

描述（申请人提供）：该项目的长期目标是了解膜蛋白复合物如何分解和降解。许多蛋白质以受调控和消耗能量的方式降解，并且被细胞识别为异常的蛋白质优先被这些“质量控制”系统靶向。虽然用于降解可溶性蛋白质的细胞机制正在变得很好理解，膜蛋白的相应过程的知识已经落后，尽管许多膜蛋白在重要过程中发挥关键作用，如信号转导，生物能量学和细胞内稳态。一些人类疾病，如囊性纤维化和视网膜色素变性，是由点突变引起的膜蛋白降解引起的。本文以单细胞绿色衣藻（Chlamydiumreinhardtii）的光系统I（PS1）复合体为模型系统。这种蛋白质是光合作用电子传递链的重要组成部分，并利用其相关叶绿素分子吸收的光来驱动电子穿过类囊体膜。它应该作为一个很好的模型底物膜蛋白降解，因为蛋白质的功能部分是在膜的平面，在那里它有许多光谱探针内置到它。该项目利用抑制基因和生物化学的互补方法。拟议继续项目的具体目标是（1）完成一组抑制突变的遗传表征，这些突变显示PS 1降解效率降低，（2）使用基于分子图谱的技术克隆代表性抑制突变，以及（3）创建生化互补系统，并将其用于纯化参与靶向和降解PS 1的蛋白质。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand how membrane protein complexes are disassembled and degraded. Many proteins are degraded in a regulated and energy-consuming fashion, and proteins recognized by the cell as aberrant are targeted by these "quality control" systems preferentially. Although the cellular mechanisms used to degrade soluble proteins are becoming well understood, knowledge of the corresponding process for membrane proteins has lagged, despite the key role many membrane proteins play in important processes, such as signal transduction, bioenergetics, and cellular homeostasis. Several human diseases, such as cystic fibrosis and retinitis pigmentosa, are caused by degradation of membrane proteins with point mutations. The model system proposed here is the Photosystem I (PS1) complex in the unicellular green alga, Chlamydomonas reinhardtii. This protein is an essential part of the photosynthetic electron transport chain and uses light absorbed by its associated chlorophyll molecules to drive electron transfer across the thylakoid membrane. It should serve as an excellent model substrate for membrane protein degradation, because the functional portion of the protein is in the plane of the membrane, where it has many spectroscopic probes built into it. The project makes use of the complementary approaches of suppressor genetics and biochemistry. The specific aims of the proposed continuation project are (1) to finish genetic characterization of a set of suppressor mutations that display decreased efficiency of degradation of PS1, (2) to clone a representative suppressor mutation using molecular map-based techniques, and (3) to create a biochemical complementation system and use it for the purification of protein(s) involved in targeting and degrading PS1.