Dubois Daniel Y, Blaise Mickaël, Becker Hubert D, Campanacci Valérie, Keith Gérard, Giegé Richard, Cambillau Christian, Lapointe Jacques, Kern Daniel
Département de Biochimie et Microbiologie, Faculté de Sciences et de Génie, Centre de Recherche sur la Fonction, la Structure et l'Ingénierie des Protéines, Université Laval, Quebec, QC, Canada G1K 7P4.
Proc Natl Acad Sci U S A. 2004 May 18;101(20):7530-5. doi: 10.1073/pnas.0401634101. Epub 2004 Apr 19.
The product of the Escherichia coli yadB gene is homologous to the N-terminal part of bacterial glutamyl-tRNA synthetases (GluRSs), including the Rossmann fold with the acceptor-binding domain and the stem-contact fold. This GluRS-like protein, which lacks the anticodon-binding domain, does not use tRNA(Glu) as substrate in vitro nor in vivo, but aminoacylates tRNA(Asp) with glutamate. The yadB gene is expressed in wild-type E. coli as an operon with the dksA gene, which encodes a protein involved in the general stress response by means of its action at the translational level. The fate of the glutamylated tRNA(Asp) is not known, but its incapacity to bind elongation factor Tu suggests that it is not involved in ribosomal protein synthesis. Genes homologous to yadB are present only in bacteria, mostly in Proteobacteria. Sequence alignments and phylogenetic analyses show that the YadB proteins form a distinct monophyletic group related to the bacterial and organellar GluRSs (alpha-type GlxRSs superfamily) with ubiquitous function as suggested by the similar functional properties of the YadB homologue from Neisseria meningitidis.
大肠杆菌yadB基因的产物与细菌谷氨酰胺-tRNA合成酶（GluRSs）的N端部分同源，包括带有受体结合结构域的罗斯曼折叠和茎接触折叠。这种类似GluRS的蛋白质缺乏反密码子结合结构域，在体外和体内均不以tRNA（Glu）为底物，而是用谷氨酸对tRNA（Asp）进行氨酰化。yadB基因在野生型大肠杆菌中作为一个操纵子与dksA基因一起表达，dksA基因编码一种通过在翻译水平上发挥作用而参与一般应激反应的蛋白质。谷氨酰化的tRNA（Asp）的命运尚不清楚，但其无法结合延伸因子Tu表明它不参与核糖体蛋白质合成。与yadB同源的基因仅存在于细菌中，主要存在于变形菌门中。序列比对和系统发育分析表明，YadB蛋白形成一个独特的单系群，与细菌和细胞器的GluRSs（α型GlxRSs超家族）相关，如脑膜炎奈瑟菌的YadB同源物的类似功能特性所表明的，它们具有普遍存在的功能。
