Inner Membrane Protein Assembly in Bacteria

细菌内膜蛋白质组装

• 批准号: 6520575
• 负责人: ROSS E DALBEY
• 金额: $ 22.12万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2005-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6520575
• 关键词: Escherichia coli; bacterial proteins; immunoprecipitation; intermolecular interaction; membrane lipids; membrane proteins; membrane reconstitution /synthesis; molecular assembly /self assembly; protein purification; temperature sensitive mutant

Protein export is fundamental to many cellular processes including secretion, organellar biogenesis, and signaling. Since hundreds to thousands of proteins must cross at least one membrane before arriving at their final destination, protein translocation is a basic process in cell biology. In prokaryotes and eukaryotes, most of the components required for efficient assembly and export of proteins into and across biological membranes are well known. In bacteria, the insertion of the majority of membrane proteins is catalyzed by a complex of proteins (SecYEG) that receives membrane protein precursors and ensures their proper distribution within the bilayer. However, there is a class of membrane proteins whose assembly occurs independently of the Sec complex. These Sec-independent membrane proteins were thought to assemble into membranes directly without the assistance of a protein complex. Recently, we discovered that the assembly of Sec-independent integral membrane proteins into the inner membrane of Escherichia coli is dependent on a new accessory protein coded by the yidC gene. YidC is a medium sized (60 kDa) integral membrane protein. Null mutations in YidC are lethal, indicating that YidC is essential for cell growth. Homologs of YidC have also been identified in mitochondria and chloroplasts. Depletion of YidC from growing cells inhibits membrane insertion of Sec-independent proteins. In addition, the assembly of Sec-dependent membrane proteins is significantly delayed, while there is no effect on the export of secreted proteins. In order to understand the role of YidC in membrane protein assembly we plan to pursue the following specific aims: (1) Examine the global role of YidC in membrane protein assembly; (2) Characterize the components involved in the YidC-dependent membrane assembly pathway; (3) Reconstitute YidC-dependent membrane assembly using purified components; and (4) Determine the sites of interaction between YidC and its substrates. These studies will help to understand this novel bacterial membrane protein assembly pathway and perhaps help to explain similar events in eukaryotic cells.

蛋白质导出是许多细胞过程的基础，包括分泌，细胞器生物发生和信号传导。由于在到达最终目的地之前必须至少跨膜越过数百至数千种蛋白质，因此蛋白质易位是细胞生物学的基本过程。在原核生物和真核生物中，有效地组装和导出蛋白质所需的大多数成分是众所周知的。在细菌中，大多数膜蛋白的插入是由蛋白质（SECYEG）催化的，该蛋白（Secyeg）接收膜蛋白前体并确保其在双层中的适当分布。但是，有一类膜蛋白的组装独立于SEC复合物。这些独立的膜蛋白被认为无需蛋白质复合物即可直接聚集到膜中。最近，我们发现，与SEC无关的整合性膜蛋白组装到大肠杆菌的内膜中取决于Yidc基因编码的新辅助蛋白。 YIDC是中型（60 kDa）积分膜蛋白。 YIDC中的无效突变是致命的，表明Yidc对于细胞生长至关重要。在线粒体和叶绿体中也已经鉴定出YIDC的同源物。 YIDC从生长细胞中耗尽会抑制SEC独立蛋白的膜插入。另外，依赖于SEC的膜蛋白的组装显着延迟，而对分泌蛋白的出口没有影响。为了了解YIDC在膜蛋白组装中的作用，我们计划追求以下特定目的：（1）检查YIDC在膜蛋白质组装中的全球作用； （2）表征与YIDC依赖性膜组件途径相关的组件； （3）使用纯化的组件重构依赖YIDC的膜组件； （4）确定Yidc及其底物之间相互作用的位点。这些研究将有助于理解这种新型的细菌膜蛋白质组装途径，并可能有助于解释真核细胞中的类似事件。