Processing the Polyprotein Precursor to Euglena LHCPII

眼虫 LHCPII 多蛋白前体的加工

• 批准号: 0224621
• 负责人: Steven Schwartzbach
• 金额: $ 0.63万
• 依托单位: University of Memphis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2004-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0224621&HistoricalAwards=false
• 关键词: Processing; Polyprotein; Precursor; Euglena; LHCPII

96-30817 Schwartzbach Most of the proteins in chloroplasts are nuclear-encoded, synthesized in the cytoplasm, and imported post-translationally into the chloroplast. Precursors of chloroplast proteins contain topogenic information for targeting to and import into chloroplasts. Precursors of Euglena light harvesting chlorophyll a/b binding protein of photosystem 11 (pLHCP11) and of the small subunit of ribulose bisphosphate carboxylase (pSSU) are polyproteins that are composed of mature polypeptides covalently linked by a conserved decapeptide. In vivo pulse chase experiments demonstrated that pLHCP11 and pSSU are transported as integral membrane proteins from the endoplasmic reticulum (ER) to the Golgi apparatus prior to chloroplast localization rather than being imported directly into the chloroplast. Once the polyproteins are in the chloroplast they are processed by an endoproteolytic polyprotein processing peptidase. PLHCP11 and pSSU each contain a signal peptide for targeting to the ER and a stop-transfer signal C-terminal of the signal peptide. Studies using canine microsomes and deletion constructs demonstrated that the stop-transfer signal anchors the protein in the membrane with the N-terminus in the microsomal lumen and the C-terminus in the cytoplasm. Previous work described the import and processing pathway of Euglena chloroplast proteins. The objective of this research is to understand the molecular mechanism of this novel trafficking pathway for Euglena chloroplast proteins. This will be achieved by developing an in vitro system that reconstitutes the Golgi apparatus to chloroplast transport event. This system should allow for the biochemical characterization of this step as well as for the identification of components that are essential for this process. This includes the isolation and characterization of the polyprotein processing peptidase(s). %%% Most of the proteins in chloroplasts are nuclear-encoded, synthesized in the cytoplasm, and imported post-translationally int o the chloroplast. Precursors of chloroplast proteins contain topogenic information for targeting to and import into chloroplasts. The objective of this research is to investigate a novel trafficking pathway for nuclear-encoded chloroplast proteins to Euglena chloroplasts. The precursors of chloroplast proteins are first targeted to the endoplasmic reticulum, transported to the Golgi apparatus and are then transported to the chloroplast. Nothing is known about the molecular mechanism of this novel trafficking pathway for precursors of chloroplast proteins to the chloroplast. ***

叶绿体中的大多数蛋白质都是核编码的，在细胞质中合成，然后翻译后输入到叶绿体中。叶绿体蛋白的前体含有定位和进入叶绿体的拓扑信息。绿藻光系统11叶绿素a/b结合蛋白（pLHCP11）和二磷酸核酮糖羧化酶小亚基（pSSU）的前体是由成熟多肽组成的多蛋白，由一个保守的十肽共价连接。体内脉冲追踪实验表明，pLHCP11和pSSU作为整体膜蛋白在叶绿体定位之前从内质网（ER）转运到高尔基体，而不是直接进入叶绿体。一旦多蛋白进入叶绿体，它们就会被内源性蛋白水解多蛋白加工肽酶处理。PLHCP11和pSSU各含有一个靶向内质网的信号肽和信号肽的停止转移信号c端。对犬微粒体和缺失构建体的研究表明，停止转移信号将蛋白锚定在膜上，n端在微粒体腔内，c端在细胞质中。以往的研究描述了绿藻叶绿体蛋白的输入和加工途径。本研究的目的是了解这一新的绿藻叶绿体蛋白转运途径的分子机制。这将通过开发一个体外系统来实现，该系统可以重建叶绿体运输事件的高尔基体。该系统应允许对该步骤进行生化表征，以及对该过程至关重要的组分的识别。这包括多蛋白加工肽酶的分离和表征。叶绿体中的大多数蛋白质是核编码的，在细胞质中合成，然后翻译后输入到叶绿体中。叶绿体蛋白的前体含有定位和进入叶绿体的拓扑信息。本研究的目的是探讨核编码叶绿体蛋白到真核植物叶绿体的一种新的运输途径。叶绿体蛋白的前体首先以内质网为靶点，转运到高尔基体，然后再转运到叶绿体。叶绿体蛋白前体到叶绿体的这种新型运输途径的分子机制尚不清楚。＊＊＊