TIC236は,クロロプラストの外側と内側の膜のトランスロコンを結びつける
Yih-Lin Chen1, Lih-Jen Chen1, Chiung-Chih Chu1
1Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Nature
|November 23, 2018
まとめ
研究者らは,外膜と内膜のトランスロコン (TOC-TIC) 機構を結びつける重要なクロロプラストタンパク質であるTIC236を特定しました. このタンパク質ブリッジは 細菌系から進化したクロロプラストの タンパク質の輸入に不可欠です
科学分野:
- クロロプラストの生物学
- タンパク質の転位
- エンドシンビオティック理論
背景:
- クロロプラストはダブル膜で シアノバクテリアから生まれました
- クロロプラストへのタンパク質の輸入は,TOCとTICの機械に依存しています.
- TOCとTICの組み立てメカニズムはほとんど不明です.
研究 の 目的:
- クロロプラストタンパク質のトランスロコン装置の組み立てに関与する部品を特定する.
- クロロプラスト包膜のタンパク質の輸入における新しい成分の役割を解明する.
主な方法:
- TICコンポーネントの識別と特徴 TIC236.
- ノックアウトとノックダウン変異体を使ったTIC236機能の分析.
- TOCとTICの成分間の相互作用を決定する生化学的測定.
- TIC236とTOC75の同類体の進化分析
主要な成果:
- 内膜タンパク質であるTIC236は,外膜チャンネルTOC75に直接結合する.
- TIC236は胚の発達に不可欠であり,そのノックダウンはTOC-TIC超複合体の形成とストロマの輸入率を減少させます.
- TIC236とTOC75は,それぞれバクテリアのTAMBとBAMAの植物特有の同種であり,共進化を示唆しています.
結論:
- ミトコンドリアとは異なり,クロロプラストのタンパク質転位には,TIC236によって形成される安定したタンパク質ブリッジが必要です.
- クロロプラストのタンパク質輸入機構は,バクテリアのTamb-BamAタンパク質分泌システムから進化した.
- TIC236は,TOC-TICトランスロコンの完全性と機能を維持する上で重要な役割を果たします.
関連する概念動画
01:11Protein Transport to the Outer Chloroplast Membrane
2.4K
Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
2.4K
01:07Anatomy of Chloroplasts
119.4K
Green algae and plants, including green stems and unripe fruit, harbor chloroplasts—the vital organelles where photosynthesis takes place. In plants, the highest density of chloroplasts is found in the mesophyll cells of leaves.
119.4K
01:18Protein Transport to the Inner Chloroplast Membrane
2.4K
Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...
2.4K
02:19Export of Mitochondrial and Chloroplast Genes
4.2K
A eukaryotic cell can have up to three different types of genetic systems: nuclear, mitochondrial, and chloroplast. During evolution, organelles have exported many genes to the nucleus; this transfer is still ongoing in some plant species. Approximately 18% of the Arabidopsis thaliana nuclear genome is thought to be derived from the chloroplast’s cyanobacterial ancestor, and around 75% of the yeast genome derived from the mitochondria’s bacterial ancestor. This export has occurred...
4.2K
02:16Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes
16.1K
The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new attributes during their evolution within eukaryotic cells. Like prokaryotic genomes, mitochondrial and chloroplast genomes neither bind with histone-like proteins nor show complex packaging into chromosome-like structures, as observed in eukaryotes. Unlike mitotic cell divisions observed in eukaryotic cells, mitochondria and chloroplasts...
16.1K
01:12Porin Insertion in the Outer Mitochondrial Membrane
4.8K
Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
4.8K