一种可能解决蛋白质进化中缺失环节的非同源氨酰-tRNA合成酶。
A noncognate aminoacyl-tRNA synthetase that may resolve a missing link in protein evolution.
作者信息
Skouloubris Stephane, Ribas de Pouplana Lluis, De Reuse Hilde, Hendrickson Tamara L
机构信息
Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
出版信息
Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11297-302. doi: 10.1073/pnas.1932482100. Epub 2003 Sep 17.
Efforts to delineate the advent of many enzymes essential to protein translation are often limited by the fact that the modern genetic code evolved before divergence of the tree of life. Glutaminyl-tRNA synthetase (GlnRS) is one noteworthy exception to the universality of the translation apparatus. In eukaryotes and some bacteria, this enzyme is essential for the biosynthesis of Gln-tRNAGln, an obligate intermediate in translation. GlnRS is absent, however, in archaea, and most bacteria, organelles, and chloroplasts. Phylogenetic analyses predict that GlnRS arose from glutamyl-tRNA synthetase (GluRS), via gene duplication with subsequent evolution of specificity. A pertinent question to ask is whether, in the advent of GlnRS, a transient GluRS-like intermediate could have been retained in an extant organism. Here, we report the discovery of an essential GluRS-like enzyme (GluRS2), which coexists with another GluRS (GluRS1) in Helicobacter pylori. We show that GluRS2's primary role is to generate Glu-tRNAGln, not Glu-tRNAGlu. Thus, GluRS2 appears to be a transient GluRS-like ancestor of GlnRS and can be defined as a GluGlnRS.
描绘蛋白质翻译过程中许多必需酶出现的努力常常受到这样一个事实的限制，即现代遗传密码在生命之树分化之前就已经进化了。谷氨酰胺-tRNA合成酶（GlnRS）是翻译装置普遍性的一个显著例外。在真核生物和一些细菌中，这种酶对于Gln-tRNAGln的生物合成至关重要，而Gln-tRNAGln是翻译过程中必不可少的中间体。然而，古细菌、大多数细菌、细胞器和叶绿体中不存在GlnRS。系统发育分析预测，GlnRS起源于谷氨酰胺-tRNA合成酶（GluRS），通过基因复制以及随后特异性的进化而来。一个相关的问题是，在GlnRS出现时，一种类似GluRS的瞬时中间体是否可能在现存生物中保留下来。在这里，我们报告了一种必需的类似GluRS的酶（GluRS2）的发现，它与另一种GluRS（GluRS1）在幽门螺杆菌中共存。我们表明，GluRS2的主要作用是生成Glu-tRNAGln，而不是Glu-tRNAGlu。因此，GluRS2似乎是GlnRS的一种瞬时类似GluRS的祖先，可以被定义为GluGlnRS。
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