Crystal structure of a small G protein in complex with the GTPase-activating protein rhoGAP
Crystal structure of a small G protein in complex with the GTPase-activating protein rhoGAP
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DOI：
10.1038/41805
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发表时间：
1997-08-14
期刊：
影响因子：
64.8
通讯作者：
Smerdon, SJ
中科院分区：
文献类型：
--
作者：
Rittinger, K;Walker, PA;Smerdon, SJ
小G蛋白转导来自质膜受体的信号以控制广泛的细胞功能(1，2)。这些蛋白质被聚集到不同的家族中，但它们都充当分子开关，在GTP结合的形式下活跃，但在GDP结合时不活跃。Rho家族的G蛋白，包括CDC42Hs，激活参与调节细胞骨架形成、细胞增殖和JNK信号通路的效应器(3-9)。G蛋白通常具有较低的固有GTP酶水解酶活性，但有一些家族特异性的GTP酶激活蛋白(GAP)可以将GTP的水解率提高10(5)倍(10，11)。本文报道了在2.7埃分辨率下，非水解性GTP类似物GMPPNP与p50ROGAP的GaP结构域形成的络合物的晶体结构。在复杂的CDC42Hs相互作用，主要通过其开关I和II区，与罗盖普上的一个浅口袋，其中排列着保守的残基。RhoGAP的Arg 85与Cdc42Hs的P-环相互作用，但来自生化数据，并通过与G-蛋白亚基G(Iα1)的类比(参考文献.12)，我们认为它在催化循环中采用了不同的构象，使其能够稳定GTP-水解反应的过渡态。
Small G proteins transduce signals from plasma-membrane receptors to control a wide range of cellular functions(1,2). These proteins are clustered into distinct families but all act as molecular switches, active in their GTP-bound form but inactive when GDP-bound. The Rho family of G proteins, which includes Cdc42Hs, activate effecters involved in the regulation of cytoskeleton formation, cell proliferation and the JNK signalling pathway(3-9). G proteins generally have a low intrinsic GTPase hydrolytic activity but there are family-specific groups of GTPase-activating proteins (GAPs) that enhance the rate of GTP hydrolysis by up to 10(5) times(10,11). We report here the crystal structure of Cdc42Hs, with the non-hydrolysable GTP analogue GMPPNP, in complex with the GAP domain of p50rhoGAP at 2.7 Angstrom resolution. In the complex Cdc42Hs interacts, mainly through its switch I and II regions, with a shallow pocket on rhoGAP which is lined with conserved residues. Arg 85 of rhoGAP interacts with the P-loop of Cdc42Hs, but from biochemical data and by analogy with the G-protein subunit G(i alpha 1) (ref. 12), we propose that it adopts a different conformation during the catalytic cycle which enables it to stabilize the transition state of the GTP-hydrolysis reaction.