Structures of the free and capped ends of the actin filament

• 成果类型: Article
• 署名作者: Carman, Peter J.; Barrie, Kyle R.; Rebowski, Grzegorz; Dominguez, Roberto
• 署名单位: University of Pennsylvania; University of Pennsylvania
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-14100
• DOI: 10.1126/science.adg6812
• 发表日期: 2023-06-23
• 页码: 1287-1292
• 关键词: particle cryo-em; barbed-end; crystal-structure; monomeric actin; adp-actin; atp-actin; refinement; mechanism; binding

摘要

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.