Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Mol Biol. 2010 Dec 17;404(5):794-802. doi: 10.1016/j.jmb.2010.10.017. Epub 2010 Oct 20.
The interaction of capping protein (CP) with actin filaments is an essential element of actin assembly and actin-based motility in nearly all eukaryotes. The dendritic nucleation model for Arp2/3-based lamellipodial assembly features capping of barbed ends by CP, and the formation of filopodia is proposed to involve inhibition of capping by formins and other proteins. To understand the molecular basis for how CP binds the barbed end of the actin filament, we have used a combination of computational and experimental approaches, primarily involving molecular docking and site-directed mutagenesis. We arrive at a model that supports all of our biochemical data and agrees very well with a cryo-electron microscopy structure of the capped filament. CP interacts with both actin protomers at the barbed end of the filament, and the amphipathic helix at the C-terminus of the β-subunit binds to the hydrophobic cleft on actin, in a manner similar to that of WH2 domains. These studies provide us with new molecular insight into how CP binds to the actin filament.
盖帽蛋白（CP）与肌动蛋白丝的相互作用是几乎所有真核生物中肌动蛋白组装和基于肌动蛋白的运动的一个基本要素。基于 Arp2/3 的片状伪足组装的树突状成核模型以 CP 对有丝分裂末端的盖帽为特征，并且提出丝状伪足的形成涉及到形成素和其他蛋白质对盖帽的抑制。为了了解 CP 如何结合肌动蛋白丝的有丝分裂末端，我们使用了计算和实验方法的组合，主要涉及分子对接和定点突变。我们得出了一个模型，该模型支持我们所有的生化数据，并与有丝分裂末端盖帽丝的低温电子显微镜结构非常吻合。CP 与丝状肌动蛋白的两个肌动蛋白原体相互作用，并且β亚基 C 末端的两亲性螺旋以类似于 WH2 结构域的方式结合到肌动蛋白的疏水性裂缝上。这些研究为我们提供了 CP 与肌动蛋白丝结合的新的分子见解。
