Structural flexibility of RNA as molecular basis for Hfq chaperone function.
Structural flexibility of RNA as molecular basis for Hfq chaperone function.
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DOI：
10.1093/nar/gks510
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发表时间：
2012-09
影响因子：
14.9
通讯作者：
Djinović-Carugo K
中科院分区：
文献类型：
--
作者：
Ribeiro Ede A Jr;Beich-Frandsen M;Konarev PV;Shang W;Vecerek B;Kontaxis G;Hämmerle H;Peterlik H;Svergun DI;Bläsi U;Djinović-Carugo K
在肠道细菌中，许多小调节RNA(SRNAs)与RNA伴侣宿主因子Q(Hfq)相关，通常需要蛋白质来调节靶mRNAs。以前的研究表明，六聚体大肠杆菌Hfq(HfqEc)与sRNAs结合在近端，而远端参与了Hfq与mRNA的相互作用。利用小角X射线散射、核磁共振和生化方法相结合的方法，我们报道了HfqEc与天然底物SSRA(DsrA34)的34个核苷酸长子序列的1：1络合物的结构分析。该sRNA参与了编码稳定期西格玛因子rpos的大肠杆菌rpos mRNA的转录后调控。HfqEc与DsrA34形成的络合物在溶液中呈现整体不对称的形状，蛋白质保持其甜甜圈状结构，而扩展的DsrA34是灵活的，表现出不同的空间排列。这些结果是通过一个模型来讨论的，其中与Hfq结合的RNA配体的结构灵活性随机地促进了碱基配对，并为Hfq固有的RNA伴侣功能提供了基础。
In enteric bacteria, many small regulatory RNAs (sRNAs) associate with the RNA chaperone host factor Q (Hfq) and often require the protein for regulation of target mRNAs. Previous studies suggested that the hexameric Escherichia coli Hfq (HfqEc) binds sRNAs on the proximal site, whereas the distal site has been implicated in Hfq–mRNA interactions. Employing a combination of small angle X-ray scattering, nuclear magnetic resonance and biochemical approaches, we report the structural analysis of a 1:1 complex of HfqEc with a 34-nt-long subsequence of a natural substrate sRNA, DsrA (DsrA34). This sRNA is involved in post-transcriptional regulation of the E. coli rpoS mRNA encoding the stationary phase sigma factor RpoS. The molecular envelopes of HfqEc in complex with DsrA34 revealed an overall asymmetric shape of the complex in solution with the protein maintaining its doughnut-like structure, whereas the extended DsrA34 is flexible and displays an ensemble of different spatial arrangements. These results are discussed in terms of a model, wherein the structural flexibility of RNA ligands bound to Hfq stochastically facilitates base pairing and provides the foundation for the RNA chaperone function inherent to Hfq.
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