ADP放出に対する滑らかな筋肉のミオシンの35-A運動がADPを放出する
M Whittaker1, E M Wilson-Kubalek, J E Smith
1Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA.
Nature
|December 14, 1995
まとめ
ミオシンIIモータータンパク質は,アクチン相互作用によって力を生み出します. 硬い軽鎖ドメインはレバーアームとして働き,筋肉の収縮中に小さなモータードメインの変化を大きな35アングストロムのステップに変換します.
科学分野:
- バイオケミストリー バイオケミストリー
- 分子生物学は分子生物学である.
- 筋肉生理学 筋肉生理学
背景:
- ミオシンII運動タンパク質は,筋肉の収縮に不可欠であり,F-アクチンフィラメントと相互作用します.
- ATPの水解を含むミオシンのパワーストロックのメカニズムは完全に理解されていません.
- 以前の研究では,クロスブリッジサイクリング中にアクチンでミオシンヘッド (S1) の移動が制限されていることが示唆されました.
研究 の 目的:
- ミオシンのパワーストロークメカニズムの構造的基礎を解明する.
- 力生成におけるミオシンS1ドメインとライトチェーン結合ドメインの役割を調査する.
- ATPの水解とアクチン結合の間にミオシンの構成の変化を決定する.
主な方法:
- 三次元 (3D) 低温電子顕微鏡 (cryo-EM) を使用して,S1-装飾されたF-アクチン構造をマッピングしました.
- ミオシンモーターの異なる状態を捕捉するために,MgADPの存在と不在で構造を決定しました.
- 詳細な構造分析では,ミオシンモータードメインと軽鎖結合ドメインの方向性を比較した.
主要な成果:
- ミオシンモータードメインの構造は,MgADP結合状態と無結合状態の間で大きく一貫していた.
- 軽鎖結合領域では,著しい指向の違いが観察されました.
- ライトチェーンの結合領域は,約23度旋回する硬いレバーアームとして機能します.
- このピボットは,約35アングストームの実質的なステップサイズをもたらします.
結論:
- ミオシンのパワーストロックは,主に軽鎖結合ドメインの回転によって引き起こされ,モータードメインの大きな形状の変化によって引き起こされません.
- ミオシンモータードメインの核酸媒介による形状の変化は,軽鎖ドメインによって増幅され,大きな動きのステップを生成します.
- このレバーアームメカニズムは,ミオシンが筋肉の収縮と細胞の運動のために効率的な力をどのように生成するのか説明します.
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