Flexural rigidity of microtubules and actin filaments measured from thermal fluctuations in shape.
Flexural rigidity of microtubules and actin filaments measured from thermal fluctuations in shape.
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微管和肌动蛋白丝的弯曲刚度是根据形状的热波动测得的。
DOI：
10.1083/jcb.120.4.923
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发表时间：
1993-02
期刊：
影响因子：
--
通讯作者：
Howard J
中科院分区：
文献类型：
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作者：
Gittes F;Mickey B;Nettleton J;Howard J
微管是长的蛋白质纤维，在真核细胞中通过定义细胞形状和作为细胞内马达蛋白的轨道来执行结构功能。我们报告的第一个精确测量的弯曲刚度的微管。通过分析其形状的热驱动波动，我们估计紫杉醇稳定的微管的平均弯曲刚度为2.2 × 10（-23）Nm 2（6.4%的不确定性）为7个未标记的微管和2.1 × 10（-23）Nm 2（4.7%的不确定性）为8个罗丹明标记的微管。这些值与早期通过对鞭毛运动建模获得的微管弯曲刚度的不太精确的估计相似。对七个罗丹明-鬼笔环肽标记的肌动蛋白丝进行类似的分析，得到了7.3 × 10（-26）Nm 2的弯曲刚度（6%的不确定性），与先前报道的结果一致。这些微管的抗弯刚度对应于5，200微米的持久长度，表明微管在细胞尺寸上是刚性的。相比之下，肌动蛋白丝的持久长度只有大约17.7微米，这也许可以解释为什么细胞内的肌动蛋白丝通常交联成束。与肌动蛋白丝相比，微管更大的抗弯刚度主要来自于前者更大的横截面。如果微管蛋白是均匀和各向同性的，那么微管的杨氏模量将是大约1.2 GPa，类似于树脂玻璃和刚性塑料。预计微管几乎是不可伸展的：细胞的顺应性主要是由于细丝弯曲或细丝之间的滑动，而不是细丝本身的伸展。
Microtubules are long, proteinaceous filaments that perform structural functions in eukaryotic cells by defining cellular shape and serving as tracks for intracellular motor proteins. We report the first accurate measurements of the flexural rigidity of microtubules. By analyzing the thermally driven fluctuations in their shape, we estimated the mean flexural rigidity of taxol-stabilized microtubules to be 2.2 x 10(-23) Nm2 (with 6.4% uncertainty) for seven unlabeled microtubules and 2.1 x 10(-23) Nm2 (with 4.7% uncertainty) for eight rhodamine-labeled microtubules. These values are similar to earlier, less precise estimates of microtubule bending stiffness obtained by modeling flagellar motion. A similar analysis on seven rhodamine-phalloidin- labeled actin filaments gave a flexural rigidity of 7.3 x 10(-26) Nm2 (with 6% uncertainty), consistent with previously reported results. The flexural rigidity of these microtubules corresponds to a persistence length of 5,200 microns showing that a microtubule is rigid over cellular dimensions. By contrast, the persistence length of an actin filament is only approximately 17.7 microns, perhaps explaining why actin filaments within cells are usually cross-linked into bundles. The greater flexural rigidity of a microtubule compared to an actin filament mainly derives from the former's larger cross-section. If tubulin were homogeneous and isotropic, then the microtubule's Young's modulus would be approximately 1.2 GPa, similar to Plexiglas and rigid plastics. Microtubules are expected to be almost inextensible: the compliance of cells is due primarily to filament bending or sliding between filaments rather than the stretching of the filaments themselves.