Solution structure of an alternate conformation of helix27 from Escherichia coli16S rRNA.
Solution structure of an alternate conformation of helix27 from Escherichia coli16S rRNA.
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DOI：
10.1002/bip.21626
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发表时间：
2011-10
期刊：
影响因子：
2.9
通讯作者：
Walter, Nils G.
中科院分区：
文献类型：
--
作者：
Spano, Meredith Newby;Walter, Nils G.
来自大肠杆菌的16S核糖体(R)RNA的Helix(H)27被称为“开关螺旋”，因为突变表明两个替代的碱基对注册可能在细菌核糖体中具有不同的功能。虽然最近的遗传分析表明H27的构象转换不是必需的，但以前的解决方案研究表明，分离的E.ColiH27可以在885和888构象之间动态转换。在这里，我们解决了一个锁定的888构象的核磁共振溶液结构。NOE和残余偶极耦合限制揭示了一种与细菌核糖体晶体结构中发现的885构象显著不同的结构。取而代之的是885构象所特有的环E基序，以及888构象不能采用的环，我们发现了通过未配对的A之间的堆积作用而稳定的不对称富含A的内环的证据。将分离的H27 888溶液结构与核糖体中的885晶体结构进行比较，表明H27的全长存在差异，这是空间限制的核糖体中没有H27构象转换的一个合理原因。
Helix (H)27 of 16S ribosomal (r)RNA from Escherichia coli was dubbed the “switch helix” when mutagenesis suggested that two alternative base pair registers may have distinct functional roles in the bacterial ribosome. Although more recent genetic analyses suggest that H27 conformational switching is not required for translation, previous solution studies demonstrated that the isolated E. coli H27 can dynamically convert between the 885 and 888 conformations. Here, we have solved the NMR solution structure of a locked 888 conformation. NOE and residual dipolar coupling restraints reveal an architecture that markedly differs from that of the 885 conformation found in crystal structures of the bacterial ribosome. In place of the loop E motif that characterizes the 885 conformer and that the 888 conformer cannot adopt, we find evidence for an asymmetrical A-rich internal loop stabilized by stacking interactions among the unpaired A’s. Comparison of the isolated H27 888 solution structure with the 885 crystal structure within the context of the ribosome suggests a difference in overall length of H27 that presents one plausible reason for the absence of H27 conformational switching within the sterically confining ribosome.
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