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首页> 外文期刊>Journal of Molecular Biology >Structure of the chloroplast signal recognition particle (SRP) receptor: Domain arrangement modulates SRP-receptor interaction
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Structure of the chloroplast signal recognition particle (SRP) receptor: Domain arrangement modulates SRP-receptor interaction

机译：叶绿体信号识别颗粒（SRP）受体的结构：域排列调节SRP-受体相互作用

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The signal recognition particle (SRP) pathway mediates co-translational targeting of nascent proteins to membranes. Chloroplast SRP is unique in that it does not contain the otherwise universally conserved SRP RNA, which accelerates the association between the SRP guanosine-5'-triphosphate (GTP) binding protein and its receptor FtsY in classical SRP pathways. Recently, we showed that the SRP and SRP receptor (SR) GTPases from chloroplast (cpSRP54 and cpFtsY, respectively) can interact with one another 400-fold more efficiently than their bacterial homologues, thus providing an explanation as to why this novel chloroplast SRP pathway bypasses the requirement for the SRP RNA. Here we report the crystal structure of cpFtsY from Arabidopsis thaliana at 2.0 angstrom resolution. In this chloroplast SR, the N-terminal "N" domain is more tightly packed, and a more extensive interaction surface is formed between the GTPase "G" domain and the N domain than was previously observed in many of its bacterial homologues. As a result, the overall conformation of apo-cpFtsY is closer to that found in the bacterial SRP center dot FtsY complex than in free bacterial FtsY, especially with regard to the relative orientation of the N and G domains. In contrast, active-site residues in the G domain are mispositioned, explaining the low basal GTP binding and hydrolysis activity of free cpFtsY. This structure emphasizes proper N-G domain arrangement as a key factor in modulating the efficiency of SRP-receptor interaction and helps account, in part, for the faster kinetics at which the chloroplast SR interacts with its binding partner in the absence of an SRP RNA. (C) 2007 Elsevier Ltd. All rights reserved.
机译：信号识别颗粒（SRP）途径介导新生蛋白对膜的共翻译靶向。叶绿体SRP的独特之处在于它不包含其他方面普遍保守的SRP RNA，从而在经典SRP途径中加速了SRP鸟苷5'-三磷酸（GTP）结合蛋白与其受体FtsY之间的缔合。最近，我们发现来自叶绿体的SRP和SRP受体（SR）GTPases（分别为cpSRP54和cpFtsY）可以比它们的细菌同源物更有效地相互作用400倍，从而提供了关于这种新型叶绿体SRP途径为何的解释绕过对SRP RNA的要求。在这里，我们报道了拟南芥中cpFtsY的晶体结构，分辨率为2.0埃。在该叶绿体SR中，与以前在许多细菌同源物中观察到的情况相比，N末端“ N”结构域更紧密地堆积，并且在GTPase“ G”结构域和N结构域之间形成了更广泛的相互作用表面。结果，apo-cpFtsY的整体构象比在细菌SRP中心点FtsY复合体中的构象要比在游离细菌FtsY中的构象更近，特别是在N和G结构域的相对方向上。相反，G域中的活性位点残基位置不正确，说明了游离cpFtsY的低基础GTP结合和水解活性。这种结构强调正确的N-G结构域排列是调节SRP-受体相互作用效率的关键因素，并部分解释了在没有SRP RNA的情况下叶绿体SR与结合伴侣相互作用的更快动力学。 （C）2007 Elsevier Ltd.保留所有权利。

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