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首页> 外文期刊>Journal of Molecular Biology >PSEUDOKNOT IN DOMAIN II OF 23 S RRNA IS ESSENTIAL FOR RIBOSOME FUNCTION
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PSEUDOKNOT IN DOMAIN II OF 23 S RRNA IS ESSENTIAL FOR RIBOSOME FUNCTION

机译：23 S RRNA的域II中的PSEUDOKNOT对核糖体功能至关重要

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The structure of domain II in all 23 S (and 23 S-like) rRNAs is constrained by a pseudoknot formed between nucleotides 1005 and 1138, and between 1006 and 1137 (Escherichia coli numbering). These nucletoides are exclusively conserved as 1005C . 1138G and 1006C . 1137G pairs in all Bacteria, Archaea and chloroplasts, whereas 1005G . 1138G and 1006U . 1137A pairs occur in Eukarya. We have mutagenised nucleotides 1005C --> G, 1006C --> U, 1137G --> A and 1138G --> C, both individually and in combinations, in a 23 S rRNA gene from the bacterium E. coli. The ability of 23 S rRNA to support cell growth is reduced when either of these base-pairs is disrupted, and it is completely abolished upon disruption of both base-pairs. Each mutant 23 S rRNA is assembled into 50 S subunits, but the mutant subunits do not stably interact with 30 S to engage in protein synthesis. Enzymatic and chemical probing of ribosomal particles reveals increased accessibility in the rRNA structure close to the sites of the mutations. The degree to which the mutations increase rRNA accessibility correlates with the severity of their phenotypic effects. Nucleotide 1131G is extremely reactive to dimethyl sulphate modification in wild-type subunits and ribosomes, but is rendered unreactive when either the pseudoknot is broken or when the r-proteins are removed. The structure of the pseudoknot region is possibly influenced by interaction of an r-protein at or close to the pseudoknot. Re-establishing the pseudoknot Watson-Crick interactions with one ''eukaryal'' (1005G . 1138C or 1006U 1137A) pair and one ''bacterial'' C G pair largely restores the structure and function of the rRNA. Bacterial ribosomes containing both these eukaryal pairs also participate in protein synthesis, although at much reduced efficiency, and the structure of their pseudoknot region is partially open and accessible. [References: 35]
机译：在所有23 S（和23 S样）rRNA中，结构域II的结构都受到核苷酸1005与1138之间以及1006与1137之间形成的假结的限制（大肠杆菌编号）。这些核苷酸专门保存为1005C。 1138G和1006C。所有细菌，古生菌和叶绿体中的1137G对，而1005G。 1138G和1006U。 Eukarya中有1137A对。在来自大肠杆菌的23 S rRNA基因中，我们分别或组合地诱变了核苷酸1005C-> G，1006C-> U，1137G-> A和1138G->C。当这些碱基对中的任何一个被破坏时，23 S rRNA支持细胞生长的能力就会降低，而当两个碱基对都被破坏时，它会被完全废除。每个突变的23 S rRNA组装成50 S的亚基，但突变的亚基不能与30 S稳定地相互作用来参与蛋白质合成。核糖体颗粒的酶促和化学探测揭示了靠近突变位点的rRNA结构中可及性的提高。突变增加rRNA可及性的程度与其表型效应的严重程度相关。核苷酸1131G对野生型亚基和核糖体中的硫酸二甲酯修饰具有极强的反应性，但当假结断裂或r蛋白被去除时，则无反应性。假结区域的结构可能受假结处或附近的r蛋白相互作用的影响。用一对“真核”（1005G，1138C或1006U 1137A）对和一个“细菌” CG对重新建立假结Watson-Crick相互作用，很大程度上恢复了rRNA的结构和功能。包含这两个真核对的细菌核糖体也参与蛋白质合成，尽管效率大大降低，而且它们的假结区的结构部分开放且易于接近。 [参考：35]

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