SERYL-TRNA SYNTHETASES: EVOLUTION AND DIVERSITY

我们将研究丝氨酰-tRNA合成酶(SerRS)的共适应。 研究了第二类氨酰-tRNA合成酶，与tRNAs的进化。这个 许多基因组序列的可用性使我们能够克隆编码基因 来自不同分类域的SerRS酶。在上一次 NIH-FIRCA赠款(支持与伊万纳博士的合作 Weygand-Durasevic)，我们专注于识别 TRNA：氨酰-tRNA合成酶的特异性 真核细胞蛋白质合成室(线粒体和 叶绿体)。直到最近，古生菌中氨基酰-tRNA合成的研究 几乎没有受到关注。第一个古生菌基因组的测序 (简氏甲烷球菌)揭示了少数典型的氨基酰tRNA的“缺乏” 合成酶，包括丝氨酸的专一性合成酶。然而，生化 纯化和异源表达的SerRS编码基因的分析 从另外两种产甲烷菌--甲烷自养甲烷杆菌和 Maripaludis，证明这些蛋白是SerRS酶。因此， 在古生菌中发现了三种类型的SerRs。这种酶来自于 嗜盐古细菌Haloarcula marismortui与 细菌SerRS蛋白，而系统发育分析在其他古生菌中发现 一个与真核生物酶序列相似的不同分支。在……里面 相比之下，这三种产甲烷古菌包含的基因只显示出低水平 与所有其他生物中已知的SERS基因序列相似并编码 一种结构上不常见的酶。在拟议的项目中，我们将进行详细的 生化、突变和结构研究，目的是阐明 这些不寻常的丝氨酰-tRNA合成酶的结构-功能关系。这些 研究将补充我们正在进行的识别和 人血清白蛋白中参与氨酰-tRNA合成的组分的表征 活生生的王国。

We will investigate the co-adaptations of seryl-tRNA synthetase (SerRS), a well studied class II aminoacyl-tRNA synthetase, with tRNAs through evolution. The availability of many genomic sequences enables us to clone the genes encoding SerRS enzymes from the different taxonomic domains. During the previous NIH-FIRCA grant (supporting the collaboration with Dr. Ivana Weygand-Durasevic), we focused on identifying the differences in tRNA:aminoacyl-tRNA synthetase specificities characteristic for the distinct protein synthesizing compartments of eukaryotic cells (mitochondria and chloroplasts). Until recently, the study of aminoacyl-tRNA synthesis in archaea had received little attention. The sequencing of the first archaeal genome (Methanococcus jannaschii) revealed the "lack" of few canonical aminoacyl-tRNA synthetases, including the one specific for serine. However, biochemical analysis of purified and heterologously expressed SerRS-encoding (serS) genes from two other methanogens, Methanoacterium thermoautotrophicum and Methanococcus maripaludis, showed that these proteins are SerRS enzymes. Thus, there are three types of SerRS found in the archaea. The enzyme from the halophilic archaeon Haloarcula marismortui has high sequence similarity to bacterial SerRS proteins, while phylogenetic analyses revealed in other archaea a different clade with sequence similarity to the eukaryotic enzymes. In contrast, the three methanogenic archaea contain genes that display only low sequence similarity to the known serS genes from all other organisms and encode a structurally uncommon enzyme. In the proposed project we will pursue detailed biochemical, mutational, and structural studies with the aim of elucidating the structure-function relationships in these unusual seryl-tRNA synthetases. These studies will complement our ongoing projects on the identification and characterization of components involved in aminoacyl-tRNA synthesis in the living kingdom.