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首页> 外文期刊>Journal of Molecular Biology >The location and the significance of a cross-link between the sarcin/ricin domain of ribosomal RNA and the elongation factor-G.
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The location and the significance of a cross-link between the sarcin/ricin domain of ribosomal RNA and the elongation factor-G.

机译：核糖体RNA的sarcin / ricin域与延伸因子-G之间交联的位置和意义。

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摘要

During translocation peptidyl-tRNA moves from the A-site to the P-site and mRNA is displaced by three nucleotides in the 3' direction. This reaction is catalyzed by elongation factor-G (EF-G) and is associated with ribosome-dependent hydrolysis of GTP. The molecular basis of translocation is the most important unsolved problem with respect to ribosome function. A critical question, one that might provide a clue to the mechanism of translocation, is the precise identity of the contacts between EF-G and ribosome components. To make the identification, a covalent bond was formed, by ultraviolet irradiation, between EF-G and a sarcin/ricin domain (SRD) oligoribonucleotide containing 5-iodouridine. The cross-link was established, by mass spectroscopy and by Edman degradation, to be between a tryptophan at position 127 in the G domain in EF-G and either one of two 5-iodouridine nucleotides in the sequence UAG2655U in the SRD. G2655 is a critical identity element for the recognition of the factor's ribosomal binding site. The site of the cross-link provides the first direct evidence that the SRD is in close proximity to the EF-G catalytic center. The proximity suggests that the SRD RNA has a role in the activation of GTP hydrolysis that leads to a transition in the conformation of the factor and to its release from the ribosome.
机译：在易位期间，肽基-tRNA从A位移动到P位，mRNA在3'方向被三个核苷酸置换。该反应被伸长因子-G（EF-G）催化，并与核糖体依赖的GTP水解有关。就核糖体功能而言，易位的分子基础是最重要的未解决的问题。一个可能为易位机制提供线索的关键问题是EF-G与核糖体组分之间接触的精确身份。为了进行鉴定，通过紫外线照射，在EF-G和含有5-碘杜里定的sarcin / ricin域（SRD）寡核糖核苷酸之间形成了共价键。通过质谱法和通过Edman降解将所述交联建立在EF-G的G结构域中的127位色氨酸与SRD中的序列UAG2655U中的两个5-碘尿苷核苷酸之一之间。 G2655是识别该因子核糖体结合位点的关键身份元件。交联的位点提供了第一个直接证据，表明SRD紧邻EF-G催化中心。邻近性表明SRD RNA在GTP水解激活中起作用，GTP水解导致因子构象转变并从核糖体释放。

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