Yeast cells select the position of their new bud at the beginning of each cell cycle. The recruitment of septins to this prospective bud site is one of the critical events in a complex assembly pathway that culminates in the outgrowth of a new daughter cell. During recruitment, septin rods follow the high concentration of Cdc42_GTP that is generated by the focused localization of the Cdc42 guanine-nucleotide-exchange factor Cdc24. We show that, shortly before budding, Cdc24 not only activates Cdc42 but also transiently interacts with Cdc11, the septin subunit that caps both ends of the septin rods. Mutations in Cdc24 that reduce affinity to Cdc11 impair septin recruitment and decrease the stability of the polarity patch. The interaction between septins and Cdc24 thus reinforces bud assembly at sites where septin structures are formed. Once the septins polymerize to form the septin ring, Cdc24 is found at the cortex of the bud and directs further outgrowth from this position.

酵母细胞在每个细胞周期开始时选择新芽的位置。将脓蛋白招募到这个预期的芽位点是复杂组装途径中的关键事件之一，最终导致新子细胞的生长。_{在募集过程中，septin 杆跟随高浓度的 Cdc42 GTP} ，该高浓度的 Cdc42 GTP是由 Cdc42 鸟嘌呤核苷酸交换因子 Cdc24 的集中定位产生的。我们发现，在出芽前不久，Cdc24 不仅激活 Cdc42，而且还短暂地与 Cdc11（覆盖隔膜棒两端的隔膜亚基）相互作用。Cdc24 中的突变降低了与 Cdc11 的亲和力，从而损害了 Septin 的募集并降低了极性贴片的稳定性。因此，septin 和 Cdc24 之间的相互作用增强了在形成 septin 结构的位点处的芽组装。一旦脓毒蛋白聚合形成脓毒蛋白环，Cdc24就会在芽的皮质处被发现，并指导从该位置进一步生长。