Role of SRP RNA in the GTPase cycles of ffh and FtsY
Role of SRP RNA in the GTPase cycles of ffh and FtsY
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DOI：
10.1021/bi011639y
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发表时间：
2001-12-18
期刊：
影响因子：
2.9
通讯作者：
Walter, P
中科院分区：
文献类型：
--
作者：
Peluso, P;Shan, SO;Walter, P
信号识别颗粒（SRP）及其受体的细菌同源物，Ffh .4.5S RNA核糖核蛋白复合物和FtsY蛋白，分别形成独特的复合物，其中Ffh和FtsY两者充当彼此的GTP酶激活蛋白，导致两种蛋白相互刺激GTP水解。先前的工作表明，4.5S RNA在Ffh和FtsY的存在下增强了GTdR活性，但尚不清楚这是如何实现的。在这项工作中，Ffh和FtsY的GTdR反应的动力学和热力学分析提供了深入了解4.5S RNA在Ffh和FtsY的GTdR循环中的作用。我们发现，4.5S RNA加速Ffh和FtsY之间的协会400倍，在他们的GTP结合形式，类似于其200倍的催化作用Ffh。先前观察到的FtsY与GppNHp结合形式的结合[Peluso，P.，等人（2000）Science 288，1640-1643]。此外，Ffh-FtsY协会是速率限制所观察到的GTdR反应与亚饱和Ffh和FtsY，从而占4.5S RNA对GTdR活性的明显刺激作用，先前观察到的。一个额外的步骤。从Ffh水解GTP。FtsY复合物，也适度促进4.5S RNA。这些结果表明，4.5S RNA调节Ffh的构象。FtsY复合物，并可能，反过来，调节其GTP酶活性在SRP功能周期。
The bacterial homologues of the signal recognition particle (SRP) and its receptor, the Ffh .4.5S RNA ribonucleoprotein complex and the FtsY protein, respectively, form a unique complex in which both Ffh and FtsY act as GTPase activating proteins for one another, resulting in the mutual stimulation of GTP hydrolysis by both proteins. Previous work showed that 4.5S RNA enhances the GTPase activity in the presence of both Ffh and FtsY, but it was not clear how this was accomplished. In this work, kinetic and thermodynamic analyses of the GTPase reactions of Ffh and FtsY have provided insights into the role of 4.5S RNA in the GTPase cycles of Ffh and FtsY. We found that 4.5S RNA accelerates the association between Ffh and FtsY 400-fold in their GTP-bound form, analogous to its 200-fold catalytic effect on Ffh . FtsY association previously observed with the GppNHp-bound form [Peluso, P., et al. (2000) Science 288, 1640-1643]. Further, Ffh-FtsY association is rate-limiting for the observed GTPase reaction with subsaturating Ffh and FtsY, thereby accounting for the apparent stimulatory effect of 4.5S RNA on the GTPase activity observed previously. An additional step. GTP hydrolysis from the Ffh . FtsY complex, is also moderately facilitated by 4.5S RNA. These results suggest that 4.5S RNA modulates the conformation of the Ffh . FtsY complex and may, in turn, regulate its GTPase activity during the SRP functional cycle.