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首页> 外文期刊>EMBO Journal >Dimerisation-dependent GTPase reaction of MnmE: how potassium acts as GTPase-activating element
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Dimerisation-dependent GTPase reaction of MnmE: how potassium acts as GTPase-activating element

机译：MnmE Dimerisation-dependent GTPase反应:充当GTPase-activating钾元素如何

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摘要

MnmE, a Guanine nucleotide-binding protein conserved between bacteria and man, is involved in the modification of tRNAs. Here we provide biochemical and X-ray structural evidence for a new GTP-hydrolysis mechanism, where the G-domains of MnmE dimerise in a potassium-dependent manner and induce GTP hydrolysis. The structure in the presence of GDP-AlFx and potassium shows how juxtaposition of the subunits induces a conformational change around the nucleotide which reorients the catalytic machinery. A critical glutamate is positioned such as to stabilise or activate the attacking water. Potassium provides a positive charge into the catalytic site in a position analogous to the arginine finger in the Ras-RasGAP system. Mutational studies show that potassium-dependent dimerisation and GTP hydrolysis can be uncoupled and that interaction between the G-domains is a prerequisite for subsequent phosphoryl transfer. We propose a model for the juxtaposition of G-domains in the full-length protein and how it induces conformational changes in the putative tRNA-modification centre.
机译：MnmE,鸟嘌呤nucleotide-binding蛋白质守恒的细菌和人之间在修改的图示。生化和x射线结构证据新的GTP-hydrolysis机制,G-domains的MnmE dimerise potassium-dependent的方式和诱导三磷酸鸟苷水解。GDP-AlFx和钾显示并列的子单元诱发构象变化的核苷酸调整催化机械。谷氨酸是稳定或等位置激活水攻击。一个正电荷的催化部位类似于的精氨酸的手指位置Ras-RasGAP系统。potassium-dependent二聚、三磷酸鸟苷水解可以非耦合相互作用G-domains之间是一个先决条件随后磷酰基转移。模型的G-domains并列完整的蛋白质,以及它如何让假定的构象变化tRNA-modification中心。

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