Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, United Kingdom.
RNA. 2013 Mar;19(3):357-64. doi: 10.1261/rna.036657.112. Epub 2013 Jan 16.
The k-turn is a widespread structural motif that introduces a tight kink into the helical axis of double-stranded RNA. The adenine bases of consecutive G•A pairs are directed toward the minor groove of the opposing helix, hydrogen bonding in a typical A-minor interaction. We show here that the available structures of k-turns divide into two classes, depending on whether N3 or N1 of the adenine at the 2b position accepts a hydrogen bond from the O2' at the -1n position. There is a coordinated structural change involving a number of hydrogen bonds between the two classes. We show here that Kt-7 can adopt either the N3 or N1 structures depending on environment. While it has the N1 structure in the ribosome, on engineering it into the SAM-I riboswitch, it changes to the N3 structure, resulting in a significant alteration in the trajectory of the helical arms.
发夹环是一种广泛存在的结构基序，它会使双链 RNA 的螺旋轴产生紧密的扭曲。连续的 G•A 对中的腺嘌呤碱基指向相反螺旋的小沟，通过典型的 A 型小沟相互作用形成氢键。我们在这里表明，发夹环的可用结构可分为两类，这取决于 2b 位置的腺嘌呤的 N3 或 N1 是否接受来自-1n 位置的 O2'的氢键。这涉及两类之间的许多氢键的协调结构变化。我们在这里表明，Kt-7 可以根据环境采用 N3 或 N1 结构。虽然它在核糖体中具有 N1 结构，但在将其工程改造为 SAM-I 核糖开关时，它会转变为 N3 结构，导致螺旋臂轨迹发生显著变化。
