一个过程性髓素与F-actin的双向结合
M L Walker1, S A Burgess, J R Sellers
1Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, UK.
Nature
|June 24, 2000
概括
髓V运动蛋白沿着一条直线沿着actin丝线移动,通过跨越actin螺旋重复. 电子显微镜揭示了myosin V的曲的领头部启动了这种定向运动.
科学领域:
- 细胞生物学 细胞生物学
- 生物化学 生物化学
- 生物物理学的生物物理.
背景情况:
- 肌氨酸是必不可少的运动蛋白,通过与活性丝相互作用,在细胞内产生力量和运动.
- 乙的螺旋结构通常导致肌运动的螺旋路径,但较长的肌头可以实现线性运动.
- 假设Myosin V具有较长的头部,可以实现线性货物运输.
研究的目的:
- 研究Myosin V的工作机制,并确定它是否在运动过程中跨越了actin螺旋重复.
- 为了阐明Myosin V沿着actin纤维线性移动的能力的结构基础.
- 为了确定Myosin V头部形状在定向运动中的作用.
主要方法:
- 使用高分辨率电子显微镜可视化了Myosin V与actin纤维的相互作用.
- 使用单颗粒处理技术分析了actin-myosin V复合物的结构和极性.
- 结构分析的重点是Myosin V头部之间的距离和它们的形状.
主要成果:
- 电子显微镜证实,工作的Myosin V分子跨越了actin螺旋重复,与大约13个actin子单元的头部分离 (范围11-15).
- 该研究揭示了一个极性结构,其中一个曲的和一个更直的Myosin V头,表明方向性.
- 单颗粒分析确定曲面头是领头,这表明它在启动工作冲动中的作用.
结论:
- 米奥辛V能够跨越行为螺旋重复,从而实现线性运动和高效的货物运输.
- 两个头部的不同形状,特别是曲的领头部,对于沿着行动丝线的定向运动至关重要.
- 这些发现提供了对Myosin V.的过程性,直线运动性的结构性见解.
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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.
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...
Generation of Straight or Branched Actin Filaments
The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
Arp2/3 Complex
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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.
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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...
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Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They are held...


