A truncated aminoacyl-tRNA synthetase modifies RNA
A truncated aminoacyl-tRNA synthetase modifies RNA
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DOI：
10.1073/pnas.0401982101
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发表时间：
2004-05-18
影响因子：
11.1
通讯作者：
Söll, D
中科院分区：
文献类型：
--
作者：
Salazar, JC;Ambrogelly, A;Söll, D
氨基酰基trna合成酶是一种模块化酶，由一个中心活性位点结构域组成，在进化过程中附加了额外的功能结构域。对细菌基因组序列的分析显示存在许多较短的氨基酰基- trna合成酶类似物。在这里，我们报道了一个高度保守的谷氨酰胺- trna合成酶（GluRS）类似物（大肠杆菌中的YadB）的特征，该类似物存在于4040种保护菌、蓝藻菌和放线菌的基因组中。大肠杆菌yadB基因编码一个截断的GluRs，该GluRs缺乏该蛋白的c端三分之一，因此缺乏反密码子结合域。对yadB的破坏表明，该基因对于大肠杆菌在丰富和最小的培养基中生长是必不可少的。与我们的不同，YadB蛋白能够在ATP存在的情况下以不依赖tRNA的方式激活谷氨酸，并将谷氨酸转移到tRNA（AsP）上。tRNA（Glu）和tRNA（Gln）都不是底物。与典型的氨基酰基tRNA不同，谷氨酸没有被酯化成tRNA的3'端腺苷。相反，它被连接到排队苷的2-氨基-5-（4,5-二羟基-2-环戊烯-1-基）部分，这个修饰的核苷占据了tRNA Asp的第一个抗结克隆位置。与典型的Glu-tRNA一样，Glutamyl-queuosine在温和的碱性处理下水解。在酸性条件下分离的tRNA分析表明，这种新的修饰存在于正常的大肠杆菌tRNA中；据推测，由于tRNA分离的标准条件包括碱性去酰化步骤，该步骤也会导致谷氨酰基- queue -甘氨酸的水解，因此它以前没有被检测到。因此，这个氨基酰基-tRNA合成酶片段有助于tRNA的标准核苷酸修饰。
Aminoacyl-tRNA synthetases are modular enzymes composed of a central active site domain to which additional functional domains were appended in the course of evolution. Analysis of bacterial genome sequences revealed the presence of many shorter aminoacyl-tRNA synthetase paralogs. Here we report the characterization of a well conserved glutamyl-tRNA synthetase (GluRS) paralog (YadB in Escherichia coli) that is present in the genomes of > 40 species of protecibacteria, cyanobacteria, and actinobacteria. The E. coli yadB gene encodes a truncated GluRs that lacks the C-terminal third of the protein and, consequently, the anticodon binding domain. Generation of a yadB disruption showed the gene to be dispensable for E. coli growth in rich and minimal media. Unlike OURS, the YadB protein was able to activate glutamate in presence of ATP in a tRNA-independent fashion and to transfer glutamate onto tRNA(AsP). Neither tRNA(Glu) nor tRNA(Gln) were substrates. In contrast to canonical aminoacyl-tRNA, glutamate was not esterified to the 3'-terminal adenosine of tRNA Asp. Instead, it was attached to the 2-amino-5-(4,5-dihydroxy-2-cyclopenten-1-yl) moiety of queuosine, the modified nucleoside occupying the firs anticoclon position of tRNA Asp. Glutamyl-queuosine, like canonical Glu-tRNA, was hydrolyzed by mild alkaline treatment. Analysis of tRNA isolated under acidic conditions showed that this novel modification is present in normal E coli tRNA; presumably it previously escaped detection as the standard conditions of tRNA isolation include an alkaline deacylation step that also causes hydrolysis of glutamyl-queuosine. Thus, this aminoacyl-tRNA synthetase fragment contributes to standard nucleotide modification of tRNA.