単一のミオシンヘッドは,アクチンフィラメントに沿って5.3ナノメートルの規則的なステップで移動します
K Kitamura1, M Tokunaga, A H Iwane
1Yanagida BioMotron Project, ERATO, JST, Mino, Osaka, Japan.
Nature
|January 29, 1999
まとめ
研究者らは,個々のミオシン分子を観察するための新しい装置を開発しました. これは,単一のミオシンヘッドが1つのATP水解サイクルで複数の急速なステップをとることができ,重要な力を発生することを明らかにしました.
科学分野:
- バイオフィジックス 生物物理学
- 分子運動力学 分子運動力学
- セルラー・フォース・ジェネレーション セルラー・フォース・ジェネレーション
背景:
- アクトミオシン (actomyosin) は,アクチン繊維とミオシン運動タンパク質で構成され,筋肉の収縮における力生成を駆動する.
- アクトミオシン力生成の離散的な機械的出来事を理解することは,細胞力学にとって極めて重要です.
- 既存の方法では,個々の分子現象を観察する解像度が不足しています.
研究 の 目的:
- 個々のミオシンサブフラグメント-1分子を捕捉し,操作できる新しい機器を開発する.
- 力の生成中に単一のミオシン分子の機械的ステップを視覚化および分析する.
- 単一分子レベルで力生成のメカニズムを解明する.
主な方法:
- シングルミオシンサブフラグメント-1分子の直接操作のためのスキャニングプローブを使用する新しい機器の開発.
- 光ラベルを使用した単一のミオシンサブフラグメント-1分子の可視化.
- ミオシン-アクチン相互作用中の位移とステップサイズの測定.
主要な成果:
- ミオシンはアクチン繊維に沿って約5.3ナノメートルの離散的な機械的なステップで動きを示した.
- 2〜5つの急速な連続したステップのグループが観察され,その結果11〜30ナノメートルのより大きな移位が発生しました.
- この複数のステップの振る舞いは,1つのATP水解サイクル内の1つのミオシンヘッドに起因する.
結論:
- この研究は,単一のATP水解サイクル中の個々のミオシンヘッドによる複数のステップの動きの直接的な証拠を提供します.
- この多段階のプロセスは,アクトミオシン系において,実質的な力および移動を発生させるための重要なメカニズムである.
- 開発された機器は,単一分子モーターのメカニズムを調査するための強力なツールを提供します.
関連する概念動画
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Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
01:15Overview of Myosin Structure and Function
Myosins are a family of molecular motor proteins, first identified in the skeletal muscles, where they are responsible for muscle contraction. Along with their role in muscle contraction, these proteins also play a role in the intracellular transport of molecules and vesicles. There are twenty-four classes of myosins based on their domain sequence and organization. Of the twenty-four, six classes (Myosin I, Myosin II, Myosin V, Myosin VI, Myosin VII, and Myosin X) have been well characterized.
01:43The Movement of Organelles and Vesicles
In eukaryotic cells, cytoskeletal filaments such as actin, microtubules, and intermediate filaments form a mesh-like cytoskeletal network. These filaments serve as tracks for transporting cellular cargo. Specialized motor proteins use the chemical energy stored in adenosine triphosphate (ATP) for this transport. During interphase, microtubules are polarized, with the plus-end towards the cell periphery and the minus-end towards the cell center. Two microtubule-associated motor proteins,...
01:18Role of Myosin in Cell Migration
Myosins are multimeric motor proteins involved in various cellular processes such as migration, adhesion, and proliferation. Myosin II is the most common type in animal cells, which binds and cross-links actin filaments.
Myosin II is a hexamer comprising two heavy chains with globular heads and coiled-coil tails, two regulatory light chains, and two essential light chains. The ATPase sites on the myosin heads hydrolyze ATP, and the released phosphate generates the force for contraction. It is...
Myosin II is a hexamer comprising two heavy chains with globular heads and coiled-coil tails, two regulatory light chains, and two essential light chains. The ATPase sites on the myosin heads hydrolyze ATP, and the released phosphate generates the force for contraction. It is...
01:26Cross-bridge Cycle
As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
01:08The Sarcomere
A sarcomere is a microscopic segment repeating in a myofibril. The sarcomere fundamentally consists of two main myofilaments: thick filaments called myosin and thin filaments called actin. These filaments interact by sliding past each other in response to stimulus. In addition to myosin and actin, several other proteins, such as tropomyosin, troponin, titin, nebulin, myomesin, α-actinin, and dystrophin, play crucial roles in regulating, structuring, and functioning of the sarcomere.
Each myosin...
Each myosin...