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首页> 外文期刊>Journal of Molecular Biology >Cofilin increases the torsional flexibility and dynamics of actin filaments.
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Cofilin increases the torsional flexibility and dynamics of actin filaments.

机译：Cofilin增加了肌动蛋白丝的扭转柔韧性和动力学。

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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 approximately 4 degrees (C = 2.30 x 10(-27) Nm2 radian(-1)) to approximately 17 degrees (C = 0.13 x 10(-27) Nm2 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 P(i) release from filaments and modulate interactions with other regulatory actin filament binding proteins.
机译：我们使用时间分辨的磷光各向异性（TPA）测量了cofilin对在Cys374上标记有赤字-碘乙乙酰胺（ErIA）的肌动蛋白丝构象和动力学的影响。 Cofilin淬灭了肌动蛋白结合的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cofilin浓度依赖性是S形的，与肌动蛋白丝的协同结合有关。各向异性的模型独立分析表明，cofilin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近邻协同作用，并在亚化学计量cofilin结合密度下达到饱和。对TPA衰减的详细分析表明，cofilin降低了肌动蛋白的抗扭刚度（C），使相邻细丝亚基之间的热驱动均方根扭转角从大约4度增加（C = 2.30 x 10（-27）Nm2弧度） （-1））在25摄氏度时达到大约17度（C = 0.13 x 10（-27）Nm2弧度（-1））。我们偏爱一种机制，其中纤溶蛋白结合会改变热ErIA-肌动蛋白丝构象异构体之间的平衡，并促进肌动蛋白的两个明显的结构变化。一种是自然界中的局部分子，它会影响肌动蛋白C末端的结构，并可能介导最近邻居的协作结合和细丝切断。第二个是肌动蛋白内部动力学的变化，它显示了非近邻的协同作用，并增加了细丝的扭转柔韧性。肌动蛋白丝对肌动蛋白的扭转动力学的远距离影响可能会加速P（i）从细丝释放，并调节与其他调节性肌动蛋白丝结合蛋白的相互作用。

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