厳格なアクチン-トロポミオシン-ミオシン複合体の構造
Elmar Behrmann1, Mirco Müller, Pawel A Penczek
1Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.
Cell
|July 24, 2012
まとめ
この研究は,筋肉の収縮の構造的基礎を明らかにし,トロポミオシンがミオシン結合を調節するためにアクチン繊維にどのように動くかを詳細に説明しています. これは,遺伝性ミオパシーについての洞察を提供します.
科学分野:
- 分子および細胞生物学
- 構造生物学 構造生物学とは
- バイオフィジックス 生物物理学
背景:
- トロポミオシンによるアクチン・ミオシン相互作用の調節は,筋肉および非筋肉細胞の収縮性にとって極めて重要です.
- トロポミオシン運動の正確な分子機構と構造的動態は,まだ完全に理解されていません.
研究 の 目的:
- アクチン-トロポミオシン-ミオシン複合体の高解像度構造を決定する.
- トロポミオシンの調節作用の基礎となる構造的再編成を解明する.
- トロポミオシン調節されたミオシンがアクチンに結合するモデルを提案する.
主な方法:
- クリオ電子顕微鏡を用いて,厳格なアクチン・トロポミオシン・ミオシン複合体の8 Åの解像度構造を決定した.
- 擬原子モデリングは,既知の結晶構造を冷凍-EM密度マップに組み込むことによって達成されました.
主要な成果:
- 複合体の詳細な構造モデルが作成され,アクチン,トロポミオシン,ミオシン間の広範なインターフェースが定義されました.
- ミオシン結合は,アクチン線維に沿ったトロポミオシンの位置の23 Åの有意なシフトを誘導することが観察されました.
- このインターフェースに影響する変異は,重度の遺伝性筋膜病変と関連しており,その機能的重要性を強調しています.
結論:
- この研究は,アクチン-ミオシン動態の調節におけるトロポミオシンの役割を理解するための構造的枠組みを提供します.
- この発見は,この複合体の変異に関連した遺伝性ミオパシーの病原性に関する分子洞察を提供します.
- 観測された構造変化に基づいて,トロポミオシン依存型ミオシン結合調節のための新しいモデルが提案されています.
関連する概念動画
Actin 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...
The 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...
Actin Polymerization
Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
Overview 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.
Formation of Higher-order Actin Filaments
The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin networks...
The high-order actin networks...
Introduction to Actin
Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution. Actin coding genes are conserved within species and across different species.


