Sharma Shivani, Grintsevich Elena E, Woo JungReem, Gurel Pinar S, Higgs Henry N, Reisler Emil, Gimzewski James K
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Langmuir. 2014 Jul 1;30(25):7533-9. doi: 10.1021/la501748x. Epub 2014 Jun 20.
Self-organization of cytoskeletal proteins such as actin and tubulin into filaments and microtubules is frequently assisted by the proteins binding to them. Formins are regulatory proteins that nucleate the formation of new filaments and are essential for a wide range of cellular functions. The vertebrate inverted formin 2 (INF2) has both actin filament nucleating and severing/depolymerizing activities connected to its ability to encircle actin filaments. Using atomic force microscopy, we report that a formin homology 2 (FH2) domain-containing construct of INF2 (INF2-FH1-FH2-C or INF2-FFC) self-assembles into nanoscale ringlike oligomeric structures in the absence of actin filaments, demonstrating an inherent ability to reorganize from a dimeric to an oligomeric state. A construct lacking the C-terminal region (INF2-FH1-FH2 or INF2-FF) also oligomerizes, confirming the dominant role of FH2-mediated interactions. Moreover, INF2-FFC domains were observed to organize into ringlike structures around single actin filaments. This is the first demonstration that formin FH2 domains can self-assemble into oligomers in the absence of filaments and has important implications for observing unaveraged decoration and/or remodeling of filaments by actin binding proteins.
细胞骨架蛋白（如肌动蛋白和微管蛋白）自组装成细丝和微管的过程通常受到与其结合的蛋白质的协助。formin是一类调节蛋白，可促使新细丝的形成，对多种细胞功能至关重要。脊椎动物反向formin 2（INF2）具有肌动蛋白丝成核以及切断/解聚的活性，这与其环绕肌动蛋白丝的能力相关。通过原子力显微镜，我们报告称，在没有肌动蛋白丝的情况下，一种含有formin同源结构域2（FH2）的INF2构建体（INF2-FH1-FH2-C或INF2-FFC）会自组装成纳米级的环状寡聚结构，证明其具有从二聚体状态重组为寡聚体状态的内在能力。一种缺少C端区域的构建体（INF2-FH1-FH2或INF2-FF）也会发生寡聚，这证实了FH2介导的相互作用起主导作用。此外，观察到INF2-FFC结构域围绕单根肌动蛋白丝组织成环状结构。这是首次证明formin FH2结构域在没有细丝的情况下能够自组装成寡聚体，对于观察肌动蛋白结合蛋白对细丝的非平均化修饰和/或重塑具有重要意义。
