ミトコンドリア内膜へのキャリアタンパク質の輸入は,Tim22によって媒介されます
C Sirrenberg1, M F Bauer, B Guiard
1Institut für Physiologische Chemie der Universität München, Germany.
Nature
|December 12, 1996
まとめ
Tim22は,ミトコンドリアのADP/ATPキャリア (AAC) 家族に不可欠な新しいタンパク質輸入成分であり,酵母におけるTim23-Tim17複合体とは独立して機能する.
科学分野:
- ミトコンドリア生物学
- プロテイン輸入機械
背景:
- ミトコンドリアタンパク質の輸入は,細胞の機能にとって極めて重要です.
- 内膜のトランスロカゼ (TIM) 機構は,タンパク質の転位を促進します.
- Tim23,Tim17,Tim44,Hsp70およびMgelは,マトリックスタンパク質の輸入に関与する既知の成分です.
研究 の 目的:
- 新しく特定されたTim22タンパク質の機能を特徴づけるため.
- 特定のミトコンドリアタンパク質の輸入におけるTim22の役割を決定する.
主な方法:
- ミトコンドリアのADP/ATPキャリア (AAC) タンパク質の輸入経路を調査した.
- Tim22の他のTIMコンポーネントとの関連を分析した.
- AACの輸入がTim23に依存し,その逆も検討した.
主要な成果:
- Tim22は,ミトコンドリアのADP/ATPキャリア (AAC) タンパク質ファミリーのインポートに不可欠です.
- AACタンパク質は,マトリックスターゲティング信号なしで合成されます.
- Tim22は,Tim23-Tim17複合体から分離した,独特の高分子量組成を形成する.
結論:
- Tim22は,ミトコンドリアタンパク質輸入機構の新しい構成要素を表しています.
- Tim22が媒介する輸入経路は,Tim23-Tim17複合体とは独立しています.
- この研究は,AAC.のような内膜タンパク質の独特の輸入経路を明らかにしています.
関連する概念動画
The 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...
Mitochondrial Protein Sorting
Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death. Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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...
Translocation 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,...
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...


