STRUCTURAL ELEMENTS THAT CONTRIBUTE TO AN UNUSUAL TERTIARY INTERACTION IN A TRANSFER-RNA
STRUCTURAL ELEMENTS THAT CONTRIBUTE TO AN UNUSUAL TERTIARY INTERACTION IN A TRANSFER-RNA
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DOI：
10.1021/bi00181a603
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发表时间：
1994-04-19
期刊：
影响因子：
2.9
通讯作者：
HOU, YM
中科院分区：
文献类型：
--
作者：
HOU, YM
转移RNA（transfer RNA，tRNA）含有一组确定的三级氢键相互作用，这些氢键相互作用建立在保守核苷酸和非保守核苷酸之间。尽管tRNA的晶体结构以详细的分子术语描述了每个三级相互作用，但对稳定三级相互作用的基本结构参数知之甚少。大肠杆菌（E.大肠杆菌）tRNA（Cys）在二氢尿苷（D）环中的G15和可变环中的G48之间具有不寻常的三级相互作用，这对于半胱氨酸氨酰化至关重要。所有其它tRNA具有嘌呤15和互补嘧啶48，其建立称为Levitt碱基对的三级相互作用[Levitt，M.（1969）Nature 224，759-763; Klug等人（1974）J. Mol. Biol. 89，511-516]。本研究中，G15.G48在E.大肠杆菌tRNA（Cys）用于研究导致其与莱维特碱基对变异的结构元件。用化学探针分析表明，D环中U21被A21取代以及D茎中核苷酸13和22之间的Watson-Crick碱基对的形成将G15.G48的氢配对转换为Levitt样G15.G48碱基对。这种开关伴随着氨酰化的催化效率降低了2个数量级。相比之下，在D或可变环中插入额外的核苷酸几乎没有影响。这些结果揭示了A21在tRNA结构中的重要性，并表明在U8.A14.A21和13.22.46位建立三级相互作用的能力增强了D-反密码子螺旋中的堆积相互作用，这是位置15和48之间三级相互作用的主要决定因素。
Transfer RNAs (tRNAs) contain a set of defined tertiary hydrogen-bonding interactions that are established between conserved and semiconserved nucleotides. Although the crystal structures of tRNAs describe each of the tertiary interactions in detailed molecular terms, little is known about the underlying structural parameters that stabilize the tertiary interactions. Escherichia coli (E. coli) tRNA(Cys) has an unusual tertiary interaction between G15 in the dihydrouridine (D) loop and G48 in the variable loop that is critical for cysteine aminoacylation. All other tRNAs have a purine 15 and a complementary pyrimidine 48 that establish a tertiary interaction known as the Levitt base pair [Levitt, M. (1969) Nature 224, 759-763; Klug et al. (1974) J. Mol. Biol. 89, 511-516]. In this study, the G15.G48 tertiary interaction in E. coli tRNA(Cys) used to investigate the structural elements that contribute to its variation from the Levitt base pair. Analysis with chemical probes showed that substitution of U21 with A21 in the D loop and formation of a Watson-Crick base pair between nucleotides 13 and 22 in the D stem switch the hydrogen-pairing of G15.G48 to a Levitt-like G15.G48 base pair. This switch was accompanied by a decrease of the catalytic efficiency of aminoacylation by 2 orders of magnitude. In contrast, insertion of additional nucleotides in the D or variable loops had little effect. The results shed new light on the significance of A21 in tRNA structure, and suggest that the ability to establish tertiary interactions at U8.A14.A21 and at positions 13.22.46 that enhances the stacking interactions in the D-anticodon helix is a major determinant for the tertiary interaction between positions 15 and 48.