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Structure and function of protein translocation and localization system

蛋白质易位和定位系统的结构和功能

基本信息

批准号：
09308021
负责人：
TOKUDA Hajime
金额：
$ 8.9万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09308021/
关键词：
proton motive force ATP secretory protein membrane translocation lipoprotein outer membrane localization 蛋白質の膜透過蛋白質の膜局在化 ABCトランスポーター Sec因子膜局在化相互作用蛋白質分泌膜小胞 SecA リポタンパク質 LolA

项目摘要

Protein translocation across the E.coli cytoplasmic membrane is catalyzed by a Sec macinery comprising six Sec factors. Among them, SecA undergoes the membrane-insertion and -deinsertion cycle upon the binding and hydrolysis of ATP, respectively. The SecA cycle is the direct driving force for protein translocation. SecG, a membrane component of the machinery, also undergoes a membrane topology inversion cycle, which is coupled to the SecA cycle. In this research project, we revealed that the SecG cycle facillitates the SecA cycle, thereby causing efficient protein translocation. Moreover, a protein motive force was also found to accerelate the SecA cycle.Maturation of lipoproteins takes place on the outer surface of the cytoplasmic membrane. Lipoproteins having other than Asp residue at the +2 position are released from the cytoplasmic membrane and localized to the outher membrane. We previously found that LolA, a lipoprotein-specific molecular chaperone in the periplasm, forms a complex with outer membrane-directed lipoprotein, but not inner membrane-specific one having Asp at +2 position. In this research project, we found that LolB and LolCDE complex are also essential for the sorting and membrane-specific localization of lipoproteins. LolB is an outer membrane receptor for lipoprotein. The LolCDE complex belongs to the ABC transport super family and mediates the release of lipoprotein from the cytoplasmic membrane.

蛋白质跨大肠杆菌细胞质膜的易位由包含六个Sec因子的Sec大分子催化。其中SecA在ATP结合和水解时分别经历膜插入和脱插入循环。SecA循环是蛋白质易位的直接驱动力。SecG，膜组件的机器，也经历了膜拓扑结构反转周期，这是耦合到SecA周期。在这个研究项目中，我们发现SecG循环促进SecA循环，从而引起有效的蛋白质易位。此外，还发现一种蛋白质动力促进SecA循环，脂蛋白的成熟发生在细胞质膜的外表面。在+2位具有非Asp残基的脂蛋白从细胞质膜释放并定位于外膜。LolA是脂蛋白特异性的分子伴侣，它与外膜脂蛋白形成复合物，但不与内膜脂蛋白形成复合物。在这个研究项目中，我们发现LolB和LolCDE复合物对于脂蛋白的分选和膜特异性定位也是必不可少的。LolB是脂蛋白的外膜受体。LolCDE复合物属于ABC转运超家族，介导脂蛋白从细胞质膜的释放。