The septins of the yeast Saccharomyces cerevisiae assemble into hetero-octameric rods by alternating interactions between neighboring G-domains or N- and C-termini, respectively. These rods polymerize end to end into apolar filaments, forming a ring beneath the prospective new bud that expands during the cell cycle into an hourglass structure. The hourglass finally splits during cytokinesis into a double ring. Understanding these transitions as well as the plasticity of the higher order assemblies requires a detailed knowledge of the underlying structures. Here we present the first X-ray crystal structure of a tetrameric Shs1-Cdc12-Cdc3-Cdc10 complex at a resolution of 3.2 Å. Close inspection of the NC-interfaces of this and other septin structures reveals a conserved contact motif that is essential for NC-interface integrity of yeast and human septins in vivo and in vitro. Using the tetrameric structure in combination with AlphaFold-Multimer allowed us to propose a model of the octameric septin rod.

酿酒酵母的隔膜通过相邻 G 结构域或 N 端和 C 端之间的交替相互作用分别组装成异八聚体杆。这些杆首尾相连地聚合成非极性细丝，在未来的新芽下方形成一个环，并在细胞周期中扩展成沙漏结构。沙漏最终在胞质分裂过程中分裂成双环。了解这些转变以及高阶组件的可塑性需要对底层结构有详细的了解。在这里，我们展示了四聚体 Shs1-Cdc12-Cdc3-Cdc10 复合物的第一个 X 射线晶体结构，分辨率为 3.2 Å。仔细检查该结构和其他败血症蛋白结构的 NC 界面，揭示了一个保守的接触基序，该基序对于酵母和人败血症蛋白在体内和体外的 NC 界面完整性至关重要。将四聚体结构与 AlphaFold-Multimer 结合使用使我们能够提出八聚化脓蛋白棒的模型。