Jiang Jun, Aduri Raviprasad, Chow Christine S, SantaLucia John
Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
Nucleic Acids Res. 2014 Apr;42(6):3971-81. doi: 10.1093/nar/gkt1329. Epub 2013 Dec 26.
Helix 69 (H69) is a 19-nt stem-loop region from the large subunit ribosomal RNA. Three pseudouridine (Ψ) modifications clustered in H69 are conserved across phylogeny and known to affect ribosome function. To explore the effects of Ψ on the conformations of Escherichia coli H69 in solution, nuclear magnetic resonance spectroscopy was used to reveal the structural differences between H69 with (ΨΨΨ) and without (UUU) Ψ modifications. Comparison of the two structures shows that H69 ΨΨΨ has the following unique features: (i) the loop region is closed by a Watson-Crick base pair between Ψ1911 and A1919, which is potentially reinforced by interactions involving Ψ1911N1H and (ii) Ψ modifications at loop residues 1915 and 1917 promote base stacking from Ψ1915 to A1918. In contrast, the H69 UUU loop region, which lacks Ψ modifications, is less organized. Structure modulation by Ψ leads to alteration in conformational behavior of the 5' half of the H69 loop region, observed as broadening of C1914 non-exchangeable base proton resonances in the H69 ΨΨΨ nuclear magnetic resonance spectra, and plays an important biological role in establishing the ribosomal intersubunit bridge B2a and mediating translational fidelity.
螺旋69（H69）是来自大亚基核糖体RNA的一个19个核苷酸的茎环区域。在H69中聚集的三个假尿苷（Ψ）修饰在系统发育中是保守的，并且已知会影响核糖体功能。为了探索Ψ对溶液中大肠杆菌H69构象的影响，利用核磁共振光谱来揭示有（ΨΨΨ）和没有（UUU）Ψ修饰的H69之间的结构差异。两种结构的比较表明，H69 ΨΨΨ具有以下独特特征：（i）环区域由Ψ1911和A1919之间的沃森-克里克碱基对封闭，这可能通过涉及Ψ1911N1H的相互作用得到加强；（ii）环残基1915和1917处的Ψ修饰促进了从Ψ1915到A1918的碱基堆积。相比之下，缺乏Ψ修饰的H69 UUU环区域的结构较松散。Ψ引起的结构调节导致H69环区域5'半部分的构象行为发生改变，这在H69 ΨΨΨ核磁共振光谱中表现为C1914非交换性碱基质子共振的变宽，并且在建立核糖体亚基间桥B2a和介导翻译保真度方面发挥重要的生物学作用。
