バクテリアのタンパク質転位過程で小分子に対する膜の障壁を保ちます
1Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Nature
|May 13, 2011
まとめ
タンパク質輸送に不可欠なSecYチャネルは,イオンなどの小さな分子に閉じ込められています. タンパク質の転位の間に,ガスケットのようなシールが形成され,膜の障壁を維持します.
科学分野:
- 分子生物学は分子生物学である.
- 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
背景:
- タンパク質が膜を横断して転移することは,細胞の機能に不可欠です.
- SecY/Sec61チャネルは,バクテリア,アルカイア,ユカリオットにおけるタンパク質輸送を促進する.
- チャンネルの砂時計構造と,膜バリア維持におけるプラグドメインの役割が議論されている.
研究 の 目的:
- Escherichia coli.におけるSecYチャネルを通じた小分子浸透のメカニズムを調査する.
- タンパク質転位の間にSecYチャネルが膜の整合性を維持する方法を決定する.
主な方法:
- 無傷なEscherichia coli細胞の野生型および変異性SecYチャネルにおける小分子浸透を研究した.
- 静止状態と,定義されたポリペプチド鎖の転位過程の両方で調べられたチャネル.
主要な成果:
- 静止状態では,SecYチャネルは孔環とプラグドメインによって封じられています.
- タンパク質の転位の間に,毛穴環はポリペプチドの周りにガセットのようなシールを形成します.
- このシールは,イオンや代謝産物などの小分子を通過するのを効果的に防ぐ.
結論:
- SecYチャネルは,孔のリングとプラグを含むダイナミックシールメカニズムを使用しています.
- このメカニズムは,タンパク質の転位の間に小分子に対する膜の不透性を確保します.
- 保存された構造は,生命のすべての領域で膜の障壁を維持するための普遍的なメカニズムを示唆しています.
関連する概念動画
Bacterial Translocation and Protein Secretion
Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Cotranslational Protein Translocation
Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Insertion of Multi-pass Transmembrane Proteins in the RER
The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
Protein Transport into the Inner Mitochondrial Membrane
Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Protein Diffusion in the Membrane
Proteins show rotational as well as lateral diffusion across the membrane. The lateral diffusion of proteins was confirmed through the cell fusion experiment where mouse and human cells were fused, resulting in hybrid cells. When the human and mouse cells fused, the specific membrane proteins on human and mouse cells were marked with the red and green-fluorescent markers, respectively. Initially, the red and green fluorescence was located on the respective hemisphere of the cell. As time...


