ミトコンドリアマトリックスにおけるhsp70の要件は,前駆体タンパク質の転位と折り畳みのためのものです
P J Kang1, J Ostermann, J Shilling
1Department of Physiological Chemistry, University of Wisconsin, Madison 53706.
Nature
|November 8, 1990
まとめ
ミトコンドリアのhsp70 (Ssc1p) は,ミトコンドリアへのタンパク質輸送に不可欠です. この熱ショックタンパク質は,前体タンパク質を膜に移動させ,ミトコンドリアマトリックス内で再折り畳むのに役立ちます.
科学分野:
- ミトコンドリア生物学 ミトコンドリア生物学
- タンパク質のバイオゲネシス
- 分子チャペロンは,分子チャペローンである.
背景:
- ミトコンドリアは,様々な機能のために核にコードされたタンパク質を輸入する.
- タンパク質の転位と折り畳みは,ミトコンドリアの完全性にとって不可欠です.
- 熱ショックタンパク質 (HSP) は,細胞のストレス反応とタンパク質ホメオスタシスにおいて重要な役割を果たします.
研究 の 目的:
- ミトコンドリアのhsp70 (Ssc1p) の機能を酵母体で調査する.
- ミトコンドリア内のタンパク質転位と折り畳みにおけるSsc1pの役割を決定する.
主な方法:
- 温度に敏感な酵母変異体の分析.
- ミトコンドリアのhsp70 (Ssc1p) の行動を研究する.
主要な成果:
- ミトコンドリアのhsp70 (Ssc1p) は,ミトコンドリアマトリックスに局限しています.
- Ssc1pは,核にコードされた前駆体タンパク質がミトコンドリア膜を横断して転位する過程に関与する.
- Ssc1pは,ミトコンドリアマトリックス内の輸入タンパク質の (再) 折り畳みを促進する.
結論:
- ミトコンドリアのhsp70 (Ssc1p) は,ミトコンドリアのタンパク質インポートに不可欠な重要な分子チャペロンです.
- Ssc1pは,タンパク質の転位と折り畳みの両方で二重の役割を果たし,適切なミトコンドリア機能を保証します.
関連する概念動画
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...
Protein Transport to the Stroma
Chloroplasts are triple membrane structures with an outer membrane, an inner membrane, and a thylakoid membrane, each containing distinct metabolite transporters, membrane translocons, and enzymes. Appropriate sorting and translocating these proteins to their correct membrane systems is essential for chloroplast function.
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...


