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首页> 外文期刊>Biochemistry >Initiator tRNA Binding by e/aIF5B,the Eukaryotic/Archaeal Homologue of Bacterial Initiation Factor IF2
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Initiator tRNA Binding by e/aIF5B,the Eukaryotic/Archaeal Homologue of Bacterial Initiation Factor IF2

机译：e / aIF5B与细菌起始因子IF2的真核/弓形同系物与启动子tRNA结合

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摘要

To carry initiator Met-tRNA_i~(Met) to the small ribosomal subunit,eukaryal and archaeal cells use a heterotrimeric factor called e/aIF2.These cells also possess a homologue of bacterial IF2 called e/aIF5B.Several results indicate that the mode of action of e/aIF5B resembles some function of bacterial IF2.The e/aIF5B factor promotes the joining of ribosomal subunits.Moreover,there is genetic evidence that the factor participates in the binding of initiator tRNA to the small ribosomal subunit.However,up to now,an interaction between e/aIF5B and initiator tRNA was not evidenced.In this study,we use an assay based on protection of aminoacyl-tRNA against spontaneous deacylation to demonstrate that archaeal aIF5B indeed can interact with initiator tRNA.In complex formation,alF5B shows specificity toward the methionyl moiety of the ligand.The complex between Saccharomyces cerevisiae elF5B and methionylated initiator tRNA is less stable than that formed with aIF5B.In addition,this complex is almost indifferent to the side chain of the esterified amino acid.These results support the idea that,beyond the channeling of Met-tRNA_i~(Met) to the 40S subunit by e/aIF2,e/aIF5B comes to interact with initiator tRNA on the ribosome.Recognition of an aminoacylated tRNA species at this site would then allow translation to begin.In the case of archaea,this checkpoint would also include the verification of the presence of a methionine at the P site.
机译：为了将启动子Met-tRNA_i〜（Met）携带到核糖体小亚基上，真核和古细菌细胞使用称为e / aIF2的异源三聚因子，这些细胞还具有细菌IF2的同系物e / aIF5B。 e / aIF5B的作用类似于细菌IF2的某些功能。e / aIF5B因子促进核糖体亚基的结合。此外，有遗传证据表明该因子参与了引发剂tRNA与小核糖体亚基的结合。目前，尚未证明e / aIF5B与启动子tRNA之间存在相互作用。在这项研究中，我们使用基于氨酰基tRNA防止自发脱酰作用的分析方法，证明古细菌aIF5B确实可以与启动子tRNA相互作用。啤酒酵母elF5B和甲硫酰化引发剂tRNA之间的复合物比与aIF5B形成的复合物不稳定，显示出对配体的甲硫酰基部分的特异性。这些结果支持了这样的观点，即除了Met-tRNA_i〜（Met）通过e / aIF2传导至40S亚基外，e / aIF5B还与启动子上的tRNA相互作用。核糖体。在此位点识别氨基酰化的tRNA物种将使翻译开始。在古细菌的情况下，该检查点还包括验证P位点是否存在甲硫氨酸。

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