運動タンパク質のミオシンIは,作業を2段階に分けて行う
C Veigel1, L M Coluccio, J D Jontes
1Department of Biology, University of York, UK.
Nature
|April 17, 1999
まとめ
単一のミオシン-I分子はアクチンを2つの異なるステップで移動し,第2のステップはアクチンの移動です.
科学分野:
- バイオケミストリー バイオケミストリー
- 細胞生物学 細胞生物学
- バイオフィジックス 生物物理学
背景:
- 細胞の運動性は,アクチン繊維と相互作用するミオシンのようなモータータンパク質に依存しています.
- ミオシンの力生成は,アクチンを結合した後の形状の変化を含むと考えられています.
- これらの機械的移行を理解することは,細胞の動きの鍵です.
研究 の 目的:
- アクチンに付着した単一のミオシンヘッドの機械的移行を測定する.
- ミオシン-Iファミリーのメンバーによって生成される段階的な動きを調査するために.
- ミオシン-アクチン相互作用の運動学とATP依存性を特徴づけるために.
主な方法:
- 単一のミオシンヘッドの動きを正確に測定するために,光学ツィーザーのトランスデューサを使用しました.
- ネズミの肝臓ミオシン-I (M(r) 130K) と鶏の腸内ブラッシュ・ボーダーミオシン-I.を研究した.
- 高時間解像度で,高速骨格筋ミオシンIIの単頭のサブフラグメント-1を検査した.
主要な成果:
- ミオシン-Iタンパク質は2つの異なるステップで動きを示します: 10 ms以内の初期 ~6 nm ステップ,変数遅延後に ~5.5 nm ステップ.
- 第2ステップ後の期間は,ATP濃度によって影響を受けます.
- 第二段階は,高速骨格筋ミオシンIIにおいて,高解像度条件下では検出できませんでした.
結論:
- ミオシンIは2段階の機械的プロセスで運動を生成します.
- ミオシン-Iのより遅い運動は,異なる機械的状態の観察を容易にする.
- これは,ミオシンモータータンパク質の動作ストロークメカニズムについての洞察を提供します.
関連する概念動画
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.
01:58Mechanical Protein Functions
Proteins perform many mechanical functions in a cell. These proteins can be classified into two general categories- proteins that generate mechanical forces and proteins that are subjected to mechanical forces. Proteins providing mechanical support to the structure of the cell, such as keratin, are subjected to mechanical force, whereas proteins involved in cell movement and transport of molecules across cell membranes, such as an ion pump, are examples of generating mechanical force.
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.
01:16Actin and Myosin in Muscle Contraction
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...
01:18Role 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...
01:20Excitation-Contraction Coupling in Skeletal Muscles
Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at the triad, a structure found in skeletal muscle fibers that comprise a T-tubule and terminal cisternae of the sarcoplasmic reticulum on each side. These triads are visible in longitudinally sectioned muscle fibers. They are typically located at the A-I junction — the junction between the A and I bands of the sarcomere.
When an action potential...
When an action potential...