デルタミュH+とATPは,前タンパク質トランスロカースの触媒サイクルの異なる段階で機能する
E Schiebel1, A J Driessen, F U Hartl
1Molecular Biology Institute, University of California, Los Angeles 90024-15.
Cell
|March 8, 1991
まとめ
E. coli の前タンパク質転位には,SecA,ATP,および膜ポテンシャルが含まれています. 電気化学的ポテンシャルがSecAが解き放たれたときの転位を駆動し,ATPがSecAが結合されたときの段階的な動きを駆動する.
科学分野:
- 細胞生物学 細胞生物学
- バイオケミストリー バイオケミストリー
- 分子生物学は分子生物学である.
背景:
- E. coliの内膜に先行してタンパク質が転移することは,タンパク質の分泌に不可欠です.
- このプロセスは,ATPの水解と陽子運動力 (PMF) のエネルギーを必要とします.
- SecAとSecYEGチャネルを含むトランスロケーション機構は,このトランスロケーションを媒介する.
研究 の 目的:
- プロテイン前転位におけるATPと膜電気化学的ポテンシャル (デルタムーH+) の異なる役割を解明する.
- SecAとデルタミューH+が協力するか,独立して行動するメカニズムを調査する.
主な方法:
- SecA,proOmpA,およびリポソームなどの精製された成分を用いたインビトロ研究.
- ATPレベルと膜ポテンシャルを操作して,転位への影響を観察する.
主要な成果:
- SecAがproOmpAとATPに結合すると,ATPの水解によりタンパク質が放出され,段階的な転位が始まります.
- 膜の電気化学的ポテンシャル (デルタ mu H+) は,SecAが解き放たれたときに急速な転位を促します.
- delta mu H+駆動の転位はSecAと非水解性ATPの類似体によって抑制され,異なるメカニズムを示唆しています.
結論:
- ATPに依存する経路とデルタミューH+依存の経路の両方が,E. coliにおけるプレタンパク質転位に寄与する.
- delta mu H+は,SecA結合から独立した急速な転位メカニズムを提供し,特にATPまたはSecAの利用可能性が低い状況下では特に効果的です.
関連する概念動画
01:58Mechanical Protein Functions
Proteins perform many mechanical functions in a cell. These proteins can be classified into two general categories- proteins that generate mechanical forces and proteins that are subjected to mechanical forces. Proteins providing mechanical support to the structure of the cell, such as keratin, are subjected to mechanical force, whereas proteins involved in cell movement and transport of molecules across cell membranes, such as an ion pump, are examples of generating mechanical force.
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
01:18ATP Synthase: Structure
ATP synthase or ATPase is among the most conserved proteins found in bacteria, mammals, and plants. This enzyme can catalyze a forward reaction in response to the electrochemical gradient, producing ATP from ADP and inorganic phosphate. ATP synthase can also work in a reverse direction by hydrolyzing ATP and generating an electrochemical gradient. Different forms of ATP synthases have evolved special features to meet the specific demands of the cell. Based on their specific feature, ATP...
01:42The ADP/ATP Carrier Protein
ADP/ATP carrier or AAC protein is the most abundant carrier protein in the inner mitochondrial membrane. It transports large quantities of ADP and ATP, equivalent to the average human body weight, every day. Among other transporters, ACC protein is one of the best-studied members of the mitochondrial carrier protein family. The ADP/ATP carrier protein comprises two transmembrane helices connected to a loop and a single alpha-helix on the matrix side. It switches between two conformational...
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:37Energy to Drive Translocation
Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
Generally, polypeptides are unfolded by two distinct...