Frustrated binding of biopolymer crosslinkers fn id=fn1 Electronic supplementary
Frustrated binding of biopolymer crosslinkers fn id=fn1 Electronic supplementary
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DOI：
10.1039/c8sm02429d
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发表时间：
2019-04-14
期刊：
影响因子：
3.4
通讯作者：
Koenderink, Gijsje H.
中科院分区：
文献类型：
--
作者：
Mulla, Yuval;Wierenga, Harmen;Koenderink, Gijsje H.
瞬时交联的肌动蛋白丝网络允许细胞结合弹性刚性和粘弹性变形的能力。半柔性聚合物网络的理论模型预测，交联剂的解键速率决定了粘弹性流动发生的时间尺度。然而，缺乏对网络和交联剂动力学的直接比较。在这里，我们使用流变学测量网络的应力松弛时间尺度，并使用光漂白后荧光恢复（FRAP）测量结合交联剂的寿命。有趣的是，我们观察到用FRAP测量的交联剂解键速率比用流变学测量的速率慢一个数量级以上。我们用三态模型来合理化这种差异，其中交联剂被绑定到0、1或2个细丝上，这使我们能够提取交联剂的过渡率，否则很难获得。我们发现单键交联剂的解键速率比双键交联剂的解键速率慢近两个数量级。我们将双结合交联剂解键率的增加归因于生物聚合物的高刚度，这阻碍了交联剂的结合。
Transiently crosslinked actin filament networks allow cells to combine elastic rigidity with the ability to deform viscoelastically. Theoretical models of semiflexible polymer networks predict that the crosslinker unbinding rate governs the timescale beyond which viscoelastic flow occurs. However a direct comparison between network and crosslinker dynamics is lacking. Here we measure the network's stress relaxation timescale using rheology and the lifetime of bound crosslinkers using fluorescence recovery after photobleaching (FRAP). Intriguingly, we observe that the crosslinker unbinding rate measured by FRAP is more than an order of magnitude slower than the rate measured by rheology. We rationalize this difference with a three-state model where crosslinkers are bound to either 0, 1 or 2 filaments, which allows us to extract crosslinker transition rates that are otherwise difficult to access. We find that the unbinding rate of singly bound crosslinkers is nearly two orders of magnitude slower than for doubly bound ones. We attribute the increased unbinding rate of doubly bound crosslinkers to the high stiffness of biopolymers, which frustrates crosslinker binding.