Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, NRW, Germany.
Mol Cell. 2009 Dec 25;36(6):1060-72. doi: 10.1016/j.molcel.2009.11.014.
Prenylated Rab proteins exist in the cytosol as soluble, high-affinity complexes with GDI that need to be disrupted for membrane attachment and targeting of Rab proteins. The Legionella pneumophila protein DrrA displaces GDI from Rab1:GDI complexes, incorporating Rab1 into Legionella-containing vacuoles and activating Rab1 by exchanging GDP for GTP. Here, we present the crystal structure of a complex between the GEF domain of DrrA and Rab1 and a detailed kinetic analysis of this exchange. DrrA efficiently catalyzes nucleotide exchange and mimics the general nucleotide exchange mechanism of mammalian GEFs for Ras-like GTPases. We show that the GEF activity of DrrA is sufficient to displace prenylated Rab1 from the Rab1:GDI complex. Thus, apparent GDI displacement by DrrA is linked directly to nucleotide exchange, suggesting a basic model for GDI displacement and specificity of Rab localization that does not require discrete GDI displacement activity.
prenylated Rab 蛋白以可溶的、高亲和力的与 GDI 形成复合物的形式存在于细胞质中，需要破坏该复合物以实现 Rab 蛋白与膜的结合和靶向。嗜肺军团菌蛋白 DrrA 从 Rab1:GDI 复合物中置换 GDI，将 Rab1 纳入含有军团菌的空泡中，并通过 GDP 与 GTP 的交换激活 Rab1。在这里，我们展示了 DrrA 的 GEF 结构域与 Rab1 之间的复合物的晶体结构，并对该交换进行了详细的动力学分析。DrrA 有效地催化核苷酸交换，并模拟了 Ras 样 GTP 酶的哺乳动物 GEF 通用核苷酸交换机制。我们表明，DrrA 的 GEF 活性足以将异戊二烯化的 Rab1 从 Rab1:GDI 复合物中置换出来。因此，DrrA 引起的 GDI 置换显然与核苷酸交换直接相关，这表明了 GDI 置换和 Rab 定位特异性的基本模型，该模型不需要离散的 GDI 置换活性。
