通过体外纳米操作直接测量有无原肌球蛋白的单根肌动蛋白丝的刚度。
Direct measurement of stiffness of single actin filaments with and without tropomyosin by in vitro nanomanipulation.
作者信息
Kojima H, Ishijima A, Yanagida T
机构信息
Bio-Motron Project, Exploratory Research for Advanced Technology, Research and Development Corporation of Japan (JRDC), Osaka.
出版信息
Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12962-6. doi: 10.1073/pnas.91.26.12962.
In order to explain the molecular mechanism of muscle contraction, it is crucial to know the distribution of the sarcomere compliance of active muscle. Here, we directly measure the stiffness of single actin filaments with and without tropomyosin, using a recently developed technique for nanomanipulation of single actin filaments with microneedles. The results show that the stiffness for 1-micron-long actin filaments with and without tropomyosin is 65.3 +/- 6.3 and 43.7 +/- 4.6 pN/nm, respectively. When the distribution of crossbridge forces along the actin filament is taken into account, the elongation of a 1-micron-long thin filament during development of isometric contraction is calculated to be approximately 0.23%. The time constant of force in response to a sudden length change is < 0.2 ms, indicating that the viscoelasticity is negligible in the millisecond time range. These results suggest that approximately 50% of the sarcomere compliance of active muscle is due to extensibility of the thin filaments.
为了解释肌肉收缩的分子机制，了解活性肌肉肌节顺应性的分布至关重要。在此，我们使用最近开发的用微针纳米操纵单根肌动蛋白丝的技术，直接测量有原肌球蛋白和无原肌球蛋白时单根肌动蛋白丝的刚度。结果表明，有和无原肌球蛋白时1微米长的肌动蛋白丝的刚度分别为65.3±6.3和43.7±4.6 pN/nm。当考虑沿肌动蛋白丝的横桥力分布时，等长收缩过程中1微米长细肌丝的伸长计算约为0.23%。对突然长度变化的力响应时间常数<0.2毫秒，表明在毫秒时间范围内粘弹性可忽略不计。这些结果表明，活性肌肉肌节顺应性的约50%归因于细肌丝的可伸展性。
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