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首页> 外文期刊>Biochemistry >The nondiscriminating aspartyl-tRNA synthetase from Helicobacter pylori: Anticodon-binding domain mutations that impact tRNA specificity and heterologous toxicity
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The nondiscriminating aspartyl-tRNA synthetase from Helicobacter pylori: Anticodon-binding domain mutations that impact tRNA specificity and heterologous toxicity

机译：幽门螺杆菌的无区别天冬氨酰-tRNA合成酶：影响tRNA特异性和异源毒性的反密码子结合域突变

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摘要

Divergent tRNA substrate recognition patterns distinguish the two distinct forms of aspartyl-tRNA synthetase (AspRS) that exist in different bacteria. In some cases, a canonical, discriminating AspRS (D-AspRS) specifically generates Asp-tRNA(Asp) and usually coexists with asparaginyl-tRNA synthetase (AsnRS). In other bacteria, particularly those that lack AsnRS, AspRS is nondiscriminating (ND-AspRS) and generates both Asp-tRNA(Asp) and the noncanonical, misacylated Asp-tRNA(Asn); this misacylated tRNA is subsequently repaired by the glutamine-dependent Asp-tRNA(Asn)/Glu-tRNA(Gln) amidotransferase (Asp/Glu-Adt). The molecular features that distinguish the closely related bacterial D-AspRS and ND-AspRS are not well-understood. Here, we report the first characterization of the ND-AspRS from the human pathogen Helicobacter pylori (H. pylori or Hp). This enzyme is toxic when heterologously overexpressed in Escherichia coli. This toxicity is rescued upon coexpression of the Hp Asp/Glu-Adt, indicating that Hp Asp/Glu-Adt can utilize E. coli Asp-tRNA(Asn) as a substrate. Finally, mutations in the anticodon-binding domain of Hp ND-AspRS reduce this enzyme's ability to misacylate tRNA(Asn), in a manner that correlates with the toxicity of the enzyme in E. coli.
机译：不同的tRNA底物识别模式区分了存在于不同细菌中的两种不同形式的天冬氨酰tRNA合成酶（AspRS）。在某些情况下，典型的区分性AspRS（D-AspRS）特异性生成Asp-tRNA（Asp），通常与天冬酰胺基tRNA合成酶（AsnRS）共存。在其他细菌中，尤其是那些缺乏AsnRS的细菌，AspRS是非歧视性的（ND-AspRS），并同时产生Asp-tRNA（Asp）和非规范的，错误酰化的Asp-tRNA（Asn）。该错误酰化的tRNA随后被谷氨酰胺依赖性Asp-tRNA（Asn）/ Glu-tRNA（Gln）酰胺基转移酶（Asp / Glu-Adt）修复。区分密切相关的细菌D-AspRS和ND-AspRS的分子特征尚未得到很好的理解。在这里，我们报道了来自人类病原体幽门螺杆菌（幽门螺杆菌或Hp）的ND-AspRS的首次表征。当在大肠杆菌中异源过量表达时，该酶是有毒的。共表达Hp Asp / Glu-Adt可以挽救这种毒性，表明Hp Asp / Glu-Adt可以利用大肠杆菌Asp-tRNA（Asn）作为底物。最后，Hp ND-AspRS的反密码子结合域中的突变降低了该酶错误修饰tRNA（Asn）的能力，其方式与该酶在大肠杆菌中的毒性有关。

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