Active Rac1 interacts with Plexin-B1:Sema4D

The cytoplasmic tails of plexins have two domains, C1 and C2, which are highly conserved and act as GAP for small GTPases like Rac1. Active Rac1 binds directly to a binding domain of Plexin-B1 in the linker region between C1 and C2. The functional consequence of the plexin-B1/Rac interaction is not understood but this binding might sequester Rac1 away from p21-activated kinase (PAK). Plexin-B1 can compete with PAK for binding to active Rac and this competition results in the ability of plexin-B1 to inhibit Rac-induced PAK activation.

Plexin 蛋白的细胞质尾部含有两个高度保守的结构域，即 C1 和 C2 结构域，它们作为小 GTP 酶如 Rac1 的 GTP 酶激活蛋白 (GAP) 功能。活性 Rac1 直接结合至 Plexin-B1 的结合域，该结合域位于 C1 和 C2 结构域之间的连接区域。Plexin-B1 与 Rac 的相互作用所引发的功能后果尚不明确，但此结合可能将 Rac1 与 p21 激活激酶 (PAK) 分隔开来。Plexin-B1 可与 PAK 竞争结合至活性 Rac，这种竞争关系使得 Plexin-B1 能够抑制 Rac 诱导的 PAK 激活。