Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Phys Rev Lett. 2009 Dec 4;103(23):238102. doi: 10.1103/PhysRevLett.103.238102. Epub 2009 Nov 30.
We examine the mechanism of bundling of cytoskeletal actin filaments by two representative bundling proteins, fascin and espin. Small-angle x-ray studies show that increased binding from linkers drives a systematic overtwist of actin filaments from their native state, which occurs in a linker-dependent fashion. Fascin bundles actin into a continuous spectrum of intermediate twist states, while espin only allows for untwisted actin filaments and fully overtwisted bundles. Based on a coarse-grained, statistical model of protein binding, we show that the interplay between binding geometry and the intrinsic flexibility of linkers mediates cooperative binding in the bundle. We attribute the respective continuous (discontinuous) bundling mechanisms of fascin (espin) to difference in the stiffness of linker bonds themselves.
我们研究了两种代表性的细胞骨架肌动蛋白丝束蛋白—— fascin 和 espin 的束丝机制。小角度 X 射线研究表明，连接物的结合增加会导致肌动蛋白丝从其天然状态下发生系统性的过度扭曲，这种扭曲是以连接物依赖的方式发生的。 fascin 将肌动蛋白束成一系列连续的中间扭曲状态，而 espin 只允许未扭曲的肌动蛋白丝和完全扭曲的束。基于蛋白质结合的粗粒度统计模型，我们表明，结合几何形状和连接物的固有灵活性之间的相互作用调节了束中的协同结合。我们将 fascin（espin）各自连续（不连续）的束丝机制归因于连接键本身的刚性差异。
