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Factors affecting the efficiency of protein secretion in E.coli.

影响大肠杆菌蛋白质分泌效率的因素。

基本信息

批准号：
06558096
负责人：
TOKUDA Hajime
金额：
$ 11.97万
依托单位：
Institute of Molecular and Cellular Biosciences, University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06558096/
关键词：
Overproduction of Sec factors Protein secretion E.coli Chaperone Precursor protein SecG Everted membrane vesicles 酸性リン脂質 SecA SecB 分泌型蛋白質蛋白質分泌装置 Sec因子大量発現

项目摘要

Preprotein translocase of E.coli comprises a peripheral component, SecA,and integral membrane components, SecY,SecE and SecG.SecA is thought to deliver the preprotein to the putative protein-conducting channel formed by SecY and SecE by undergoing ATP-driven cycles of membrane insertion and deinsertion. SecG renders the translocase highly efficient by unknown mechanism. Preprotein translocation into everted membrane vesicles is inhibited by an externally added antibody raised against the C-terminal region of SecG.However, we found that this region is exposed to the inside (periplasmic side) of membrane vesicles in the absence of preprotein translocation, thereby being protected from external proteinase K.Surprisingly, when preprotein translocation was started with ATP hydrolysis, the C-terminal region was exposed to the outside (cytoplasmic side) of membrane vesicles and thus digested by proteinase K.Another region of SecG showed a change in membrane sidedness, from the cytoplasmic to the periplasmic side, upon preprotein translocation, indicating that SecG undergoes topology inversion. This topology inversion was tightly coupled to the SecG function, and linked with the insertion-deinsertion cycle of SecA.We propose here that the inversion cycle of the SecG topology facilitates the insertion-deinsertion cycle of SecA,thereby causing efficient preprotein translocation.

大肠杆菌的前蛋白转位酶由外周组分SecA和完整的膜组分SecY、SecE和SecG组成，SecA被认为通过ATP驱动的膜插入和脱嵌循环将前蛋白递送到由SecY和SecE形成的推定的蛋白传导通道。SecG通过未知的机制使易位酶高效。前蛋白转位到外翻的膜囊泡中被外部添加的抗SecG C-末端区域的抗体所抑制。令人惊讶的是，当前蛋白易位开始与ATP水解，C-末端区域暴露于膜囊泡的外部（细胞质侧），并因此被蛋白酶K消化。SecG的另一区域显示出在前蛋白易位时膜侧性从细胞质侧到周质侧的变化，表明SecG经历拓扑结构倒位。这种拓扑结构的倒位与SecG的功能紧密相连，并与SecA的插入-脱插入循环相关联。我们认为，SecG拓扑结构的倒位循环促进了SecA的插入-脱插入循环，从而导致了前蛋白的高效转位。