Deniziak Marzanna, Sauter Claude, Becker Hubert Dominique, Paulus Caroline Alexandra, Giegé Richard, Kern Daniel
UPR 9002 Architecture et Reactivité de l'ARN, Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15, Rue René Descartes, F-67084 Strasbourg Cedex, France.
Nucleic Acids Res. 2007;35(5):1421-31. doi: 10.1093/nar/gkl1164. Epub 2007 Feb 6.
Glutaminyl-tRNA synthetase from Deinococcus radiodurans possesses a C-terminal extension of 215 residues appending the anticodon-binding domain. This domain constitutes a paralog of the Yqey protein present in various organisms and part of it is present in the C-terminal end of the GatB subunit of GatCAB, a partner of the indirect pathway of Gln-tRNA(Gln) formation. To analyze the peculiarities of the structure-function relationship of this GlnRS related to the Yqey domain, a structure of the protein was solved from crystals diffracting at 2.3 A and a docking model of the synthetase complexed to tRNA(Gln) constructed. The comparison of the modeled complex with the structure of the E. coli complex reveals that all residues of E. coli GlnRS contacting tRNA(Gln) are conserved in D. radiodurans GlnRS, leaving the functional role of the Yqey domain puzzling. Kinetic investigations and tRNA-binding experiments of full length and Yqey-truncated GlnRSs reveal that the Yqey domain is involved in tRNA(Gln) recognition. They demonstrate that Yqey plays the role of an affinity-enhancer of GlnRS for tRNA(Gln) acting only in cis. However, the presence of Yqey in free state in organisms lacking GlnRS, suggests that this domain may exert additional cellular functions.
来自耐辐射球菌的谷氨酰胺-tRNA合成酶在其反密码子结合结构域后有一个215个残基的C末端延伸。该结构域构成了存在于多种生物中的Yqey蛋白的旁系同源物,并且其一部分存在于Gln-tRNA(Gln)形成间接途径的伙伴GatCAB的GatB亚基的C末端。为了分析与Yqey结构域相关的这种谷氨酰胺合成酶的结构-功能关系的特殊性,解析了该蛋白在2.3 Å分辨率下衍射晶体的结构,并构建了该合成酶与tRNA(Gln)复合的对接模型。将模拟复合物与大肠杆菌复合物的结构进行比较,结果表明大肠杆菌谷氨酰胺合成酶中所有与tRNA(Gln)接触的残基在耐辐射球菌谷氨酰胺合成酶中都是保守的,这使得Yqey结构域的功能作用令人费解。对全长和Yqey截短的谷氨酰胺合成酶的动力学研究和tRNA结合实验表明,Yqey结构域参与tRNA(Gln)的识别。这些研究表明,Yqey仅以顺式作用发挥谷氨酰胺合成酶对tRNA(Gln)的亲和力增强剂的作用。然而,在缺乏谷氨酰胺合成酶的生物中Yqey以游离状态存在,这表明该结构域可能发挥额外的细胞功能。