Nassar N, Hoffman G R, Manor D, Clardy J C, Cerione R A
Department of Pharmacology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
Nat Struct Biol. 1998 Dec;5(12):1047-52. doi: 10.1038/4156.
The Rho-related small GTP-binding protein Cdc42 has a low intrinsic GTPase activity that is significantly enhanced by its specific GTPase-activating protein, Cdc42GAP. In this report, we present the tertiary structure for the aluminum fluoride-promoted complex between Cdc42 and a catalytically active domain of Cdc42GAP as well as the complex between Cdc42 and the catalytically compromised Cdc42GAP(R305A) mutant. These structures, which mimic the transition state for the GTP hydrolytic reaction, show the presence of an AIF3 molecule, as was seen for the corresponding Ras-p120RasGAP complex, but in contrast to what has been reported for the Rho-Cdc42GAP complex or for heterotrimeric G protein alpha subunits, where AIF4- was observed. The Cdc42GAP stabilizes both the switch I and switch II domains of Cdc42 and contributes a highly conserved arginine (Arg 305) to the active site. Comparison of the structures for the wild type and mutant Cdc42GAP complexes provides important insights into the GAP-catalyzed GTP hydrolytic reaction.
Rho相关的小GTP结合蛋白Cdc42具有较低的内在GTP酶活性，其特异性GTP酶激活蛋白Cdc42GAP可显著增强该活性。在本报告中，我们展示了Cdc42与Cdc42GAP催化活性结构域之间氟化铝促进复合物以及Cdc42与催化受损的Cdc42GAP(R305A)突变体之间复合物的三级结构。这些模拟GTP水解反应过渡态的结构显示存在一个AIF3分子，这与相应的Ras-p120RasGAP复合物情况相同，但与Rho-Cdc42GAP复合物或异源三聚体G蛋白α亚基的报道情况相反，后者观察到的是AIF4-。Cdc42GAP稳定了Cdc42的开关I和开关II结构域，并为活性位点贡献了一个高度保守的精氨酸（Arg 305）。野生型和突变型Cdc42GAP复合物结构的比较为GAP催化的GTP水解反应提供了重要见解。
