ミトコンドリアタンパク質の輸入:外膜のトランス側におけるプレシーケンスの可逆結合は,部分的な転位と展開を促します
1Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie, Universität München, Federal Republic of Germany.
Cell
|January 13, 1995
まとめ
ミトコンドリアタンパク質の輸入は,外膜部位への連続結合を伴い,前タンパク質の転位と展開を促します. 完成には内膜エネルギーが必要で,前列は標的と動きに不可欠である.
科学分野:
- ミトコンドリア生物学 ミトコンドリア生物学
- タンパク質の輸入と転移
- 細胞膜のダイナミクス
背景:
- ミトコンドリアの機能には精密なタンパク質の輸入が必要です.
- ミトコンドリア外膜 (MOM) は,選択的障壁として作用する.
- MOMにおけるプレタンパク質転位のメカニズムは複雑である.
研究 の 目的:
- MOMにおけるマトリックス標的型前タンパク質転位のメカニズムを解明する.
- 特定の結合部位の役割と,このプロセスにおける前配列を特定する.
- 輸入中のMOMと内膜システムの相互作用を理解する.
主な方法:
- 純化された外膜膀をインビトロ研究に使用した.
- 前タンパク質の連続的および可逆的結合相互作用を調査した.
- 転位におけるcisおよびtrans結合部位の役割を分析した.
主要な成果:
- MOMの2つの連続および可逆結合部位 (cisとtrans) を特定しました.
- トランスサイトへの結合がタンパク質前転位と展開を開始することを示した.
- 転位には内膜のエネルギーシステムとの結合が必要であることが示された.
- ターゲティングとトランスロケーションの両方でN端前列の重要な役割を確認しました.
結論:
- ミトコンドリアのタンパク質輸入機構は,前タンパク質の移動を促進する転位チャネルを形成する.
- このチャネルは,膜内のタンパク質の横向的集積を防止します.
- 前配列は,MOM全体で効率的なターゲティングとトランスロケーションに不可欠です.
関連する概念動画
Mitochondrial Protein Sorting
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Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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Mitochondrial Precursor Proteins
Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70 chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Most of the mitochondrial precursors...
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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,...
Energy 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...
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 Translocation Machinery on the ER Membrane
The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.


