ミトコンドリアTIM23複合体の光マッピングは,水面,基板と相互作用するヘリックス表面を明らかにします
Nathan N Alder1, Robert E Jensen, Arthur E Johnson
1Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA.
Cell
|August 12, 2008
まとめ
研究者は,光探査機を使用してミトコンドリア内のTIM23複合チャネルの構造をマッピングしました. これは,インポート中にタンパク質がミトコンドリア内膜をどのように通過するかを明らかにします.
科学分野:
- ミトコンドリア生物学 ミトコンドリア生物学
- タンパク質の輸送
- 膜バイオフィジックス
背景:
- ミトコンドリア内膜のタンパク質転位は,細胞機能にとって極めて重要であり,TIM23複合体によって媒介されます.
- Tim23サブユニットの正確な構造,特にタンパク質伝導チャネルを形成する領域は,ほとんど不明のままです.
研究 の 目的:
- 健全なミトコンドリアにおける機能的なTIM23複合体内のTim23サブユニットの高解像度構造と環境を調査する.
- 輸入タンパク質と相互作用するTim23の領域を特定し,チャネルゲートメカニズムを理解する.
主な方法:
- 環境に敏感な光探査機を使用し,それぞれがTim23誘導体の特定の場所にあり,機能的なTIM23複合体に統合されています.
- 活性ミトコンドリア内の探査環境を分析するために複数のスペクトルテクニックを使用しました.
- 光データとクロスリンク研究を組み合わせて,タンパク質伝導チャネル内の探査機の位置をマップします.
主要な成果:
- Tim23のトランスメブラン領域内のアルファヘリル構造を特定し,両生環境に位置しています.
- タンパク質の輸入中に水面ヘリクサ面のプローブに特定のスペクトル変化が観察され,ダイナミックな構造的変化を示しています.
- 消火剤への探査機のアクセシビリティを評価し,チャネルゲーティングプロセスに関する洞察を提供しました.
結論:
- 完全に機能する,膜に埋め込まれた複合体内のトランスロコンチャネル構造の前例のない高解像度ビューを提供しました.
- TIM23チャネルを通じたタンパク質転位の構造的基礎を明らかにし,その動的調節に関する洞察を提供しました.
- 膜タンパク質複合体を in situ で研究するためのサイト固有の光探査機の有用性を実証しました.
関連する概念動画
01:28The Inner Mitochondrial Membrane
The inner mitochondrial membrane is the primary site of ATP synthesis. The inner membrane domain that forms a smooth layer adjacent to the outer membrane is called the inner boundary membrane. This domain contains membrane transporters that drive metabolites in and out of the mitochondria. In contrast, the inner membrane network that invaginates into the matrix space is called the cristae membrane. This domain accounts for principle mitochondrial function as it accommodates the protein...
01:39Mitochondrial 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...
01:19Translocation 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,...
01:37Energy 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...
01:12Porin Insertion in the Outer Mitochondrial Membrane
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...
01:34Protein 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...