Structural and energetic analysis of metal ions essential to SRP signal recognition domain assembly
Structural and energetic analysis of metal ions essential to SRP signal recognition domain assembly
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DOI：
10.1021/bi026163c
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发表时间：
2002-10-01
期刊：
影响因子：
2.9
通讯作者：
Doudna, JA
中科院分区：
文献类型：
--
作者：
Batey, RT;Doudna, JA
信号识别颗粒（SRP）通过与疏水信号序列结合，将蛋白质靶向真核生物的内质网或原核生物的内膜。信号肽识别发生在SRP高度保守的RNA - 蛋白质核心内，这凸显了该复合物在SRP功能中的重要性。对处于游离态和结合态的原核生物SRP的RNA和蛋白质成分进行的结构分析表明，RNA在蛋白质结合时会发生显著的构象变化，涉及吸收几种单价和二价阳离子。为了研究这些金属离子在功能性SRP复合物形成中的作用，我们使用结合亲和力测定和X射线晶体学来分析结合在RNA中的单价和二价金属离子的特异性以及能量贡献。我们的结果表明，几个对RNA构象很重要的金属离子结合位点可以容纳化学性质不同的离子，且通常不影响复合物的结构。因此，虽然这些金属离子排列有序，对SRP复合物的形成和稳定性至关重要，但它们的行为类似于非特异性金属离子。
The signal recognition particle (SRP) targets proteins to the endoplasmic reticulum in eukaryotes or to the inner membrane in prokaryotes by binding to hydrophobic signal sequences. Signal peptide recognition occurs within the highly conserved RNA-protein core of the SRP, underscoring the importance of this complex in SRP function. Structural analysis of the RNA and protein components of the prokaryotic SRP in the free and bound states revealed that the RNA undergoes a significant conformational change upon protein binding involving the uptake of several monovalent and divalent cations. To investigate the role of these metal ions in formation of the functional SRP complex, we used binding affinity assays and X-ray crystallography to analyze the specificity and energetic contributions of mono- and divalent metal ions bound in the RNA. Our results demonstrate that several metal ion binding sites important for RNA conformation can accommodate chemically distinct ions, often without affecting the structure of the complex. Thus, while these metal ions are highly ordered and essential for the formation and stability of the SRP complex, they behave like nonspecific metal ions.