PDF(Pubmed)
Abstract：
The barbed and pointed ends of the actin filament (F-actin) are the sites of growth and shrinkage and the targets of capping proteins that block subunit exchange, including CapZ at the barbed end and tropomodulin at the pointed end. We describe cryo-electron microscopy structures of the free and capped ends of F-actin. Terminal subunits at the free barbed end adopt a \"flat\" F-actin conformation. CapZ binds with minor changes to the barbed end but with major changes to itself. By contrast, subunits at the free pointed end adopt a \"twisted\" monomeric actin (G-actin) conformation. Tropomodulin binding forces the second subunit into an F-actin conformation. The structures reveal how the ends differ from the middle in F-actin and how these differences control subunit addition, dissociation, capping, and interactions with end-binding proteins.
摘要：
肌动蛋白丝（F-actin）的倒钩和尖端是生长/收缩的位点，也是阻断亚基交换的加帽蛋白的靶标，包括带刺末端的CapZ和尖端的rotomodulin。我们描述了F-肌动蛋白的游离端和加帽端的低温电子显微镜结构。自由带刺末端的末端亚基采用“扁平”F-肌动蛋白构象。CapZ与带刺末端的微小变化结合，但与自身的重大变化结合。相比之下,游离尖端的亚基采用“扭曲的”G-肌动蛋白构象。原调节素结合迫使第二亚基进入F-肌动蛋白构象。这些结构揭示了F-肌动蛋白的末端与中间的不同，以及这些差异如何控制亚基的添加/解离，capping,以及与末端结合蛋白的相互作用。
