通过体外显微操作直接测量单根肌动蛋白丝的抗扭刚度和扭转下肌动蛋白-肌动蛋白键的断裂力。
Torsional rigidity of single actin filaments and actin-actin bond breaking force under torsion measured directly by in vitro micromanipulation.
作者信息
Tsuda Y, Yasutake H, Ishijima A, Yanagida T
机构信息
Department of Anesthesiology, Osaka University Medical School, Japan.
出版信息
Proc Natl Acad Sci U S A. 1996 Nov 12;93(23):12937-42. doi: 10.1073/pnas.93.23.12937.
Knowledge of the elastic properties of actin filaments is crucial for considering its role in muscle contraction, cellular motile events, and formation of cell shape. The stiffness of actin filaments in the directions of stretching and bending has been determined. In this study, we have directly determined the torsional rigidity and breaking force of single actin filaments by measuring the rotational Brownian motion and tensile strength using optical tweezers and microneedles, respectively. Rotational angular fluctuations of filaments supplied the torsional rigidity as (8.0 +/- 1.2) x 10(-26) Nm2. This value is similar to that deduced from the longitudinal rigidity, assuming the actin filament to be a homogeneous rod. The breaking force of the actin-actin bond was measured while twisting a filament through various angles using microneedles. The breaking force decreased greatly under twist, e.g., from 600-320 pN when filaments were turned through 90 degrees, independent of the rotational direction. Our results indicate that an actin filament exhibits comparable flexibility in the rotational and longitudinal directions, but breaks more easily under torsional load.
了解肌动蛋白丝的弹性特性对于理解其在肌肉收缩、细胞运动事件以及细胞形状形成中的作用至关重要。已经测定了肌动蛋白丝在拉伸和弯曲方向上的刚度。在本研究中，我们分别使用光镊和微针测量旋转布朗运动和拉伸强度，直接测定了单个肌动蛋白丝的扭转刚度和断裂力。丝的旋转角波动提供的扭转刚度为(8.0±1.2)×10⁻²⁶ N·m²。假设肌动蛋白丝为均匀杆，该值与从纵向刚度推导出的值相似。使用微针在以不同角度扭转丝的同时测量肌动蛋白-肌动蛋白键的断裂力。在扭转下断裂力大幅下降，例如，当丝旋转90度时，从600 - 320 pN下降，与旋转方向无关。我们的结果表明，肌动蛋白丝在旋转和纵向方向上表现出相当的柔韧性，但在扭转载荷下更容易断裂。
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