Cofilin increases the torsional flexibility and dynamics of actin filaments
Cofilin increases the torsional flexibility and dynamics of actin filaments
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DOI：
10.1016/j.jmb.2005.09.021
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发表时间：
2005-11-11
影响因子：
5.6
通讯作者：
De La Cruz, EM
中科院分区：
文献类型：
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作者：
Prochniewicz, E;Janson, N;De La Cruz, EM
我们使用时间分辨磷光各向异性 (TPA) 测量了肌动蛋白丝切蛋白对用赤藓红-碘乙酰胺 (ErIA) 在 Cys374 标记的肌动蛋白丝的构象和动力学的影响。 Cofilin 猝灭肌动蛋白结合的 ErIA 的磷光强度，表明结合改变了探针的局部环境。磷光强度的肌丝蛋白丝切蛋白浓度依赖性是S形的，与协同肌动蛋白丝结合一致。各向异性的模型独立分析表明，丝切蛋白增加了肌动蛋白微秒旋转运动的速率。与磷光强度的降低相反，旋转运动速率的变化显示出非最近邻协作相互作用，并且在亚化学计量丝切蛋白结合密度下饱和。 TPA 衰减的详细分析表明，丝切蛋白降低了肌动蛋白的扭转刚度 (C)，将相邻丝亚基之间的热驱动均方根扭转角从大约 4 度 (C = 2.30 X 10(-27) Nm(2) 弧度(-1)) 增加到大约 17 度 (C=0.13X 10(-27) Nm(2)弧度（-1））在25摄氏度。我们赞成肌丝蛋白丝切蛋白结合改变热ErIA-肌动蛋白丝构象异构体之间的平衡的机制，并促进肌动蛋白中两种不同的结构变化。一种是局部的，它影响肌动蛋白 C 末端的结构，并可能介导最近邻合作结合和丝切断。第二个是肌动蛋白内部动力学的变化，它表现出非最近邻协同性并增加了丝的扭转柔韧性。丝切蛋白对肌动蛋白扭转动力学的远程影响可能会加速 Pi 从丝中释放，并调节与其他调节性肌动蛋白丝结合蛋白的相互作用。 (c) 2005 Elsevier Ltd. 保留所有权利。
We have measured the effects of cofilin on the conformation and dynamics of actin filaments labeled at Cys374 with erythrosin-iodoacetemide (ErIA), using time-resolved phosphorescence anisotropy (TPA). Cofilin quenches the phosphorescence intensity of actin-bound ErIA, indicating that binding changes the local environment of the probe. The cofilin concentration-dependence of the phosphorescence intensity is sigmoidal, consistent with cooperative actin filament binding. Model-independent analysis of the anisotropies indicates that cofilin increases the rates of the microsecond rotational motions of actin. In contrast to the reduction in phosphorescence intensity, the changes in the rates of rotational motions display non-nearest-neighbor cooperative interactions and saturate at substoichiometric cofilin binding densities. Detailed analysis of the TPA decays indicates that cofilin decreases the torsional rigidity (C) of actin, increasing the thermally driven root-mean-square torsional angle between adjacent filament subunits from similar to 4 degrees (C = 2.30 X 10(-27) Nm(2) radian(-1)) to similar to 17 degrees (C=0.13X 10(-27) Nm(2) radian(-1)) at 25 degrees C. We favor a mechanism in which cofilin binding shifts the equilibrium between thermal ErIA-actin filament conformers, and facilitates two distinct structural changes in actin. One is local in nature, which affects the structure of actin's C terminus and is likely to mediate nearest-neighbor cooperative binding and filament severing. The second is a change in the internal dynamics of actin, which displays non-nearest-neighbor cooperativity and increases the torsional flexibility of filaments. The long-range effects of cofilin on the torsional dynamics of actin may accelerate Pi release from filaments and modulate interactions with other regulatory actin filament binding proteins. (c) 2005 Elsevier Ltd. All rights reserved.