SERYL-TRNA SYNTHETASES: EVOLUTION AND DIVERSITY

我们将研究丝氨酰-tRNA合成酶（SerRS）的共适应性， 研究II类氨酰-tRNA合成酶，通过进化与tRNA。的 许多基因组序列的可用性使我们能够克隆编码 来自不同分类学域的SerRS酶。前一 NIH-FIRCA补助金（支持与Ireland博士的合作 Weygand-Durasevic），我们专注于识别 tRNA：氨酰-tRNA合成酶特异性， 真核细胞的蛋白质合成区室（线粒体和 叶绿体）。直到最近，古细菌中氨酰-tRNA合成的研究 很少受到关注。第一个古细菌基因组的测序 （甲烷球菌jannaschii）揭示了“缺乏”几个典型的氨酰-tRNA 合成酶，包括对丝氨酸特异的合成酶。然而，生物化学 纯化和异源表达的SerRS编码（Sers）基因的分析 来自另外两种产甲烷菌，热自养甲烷杆菌和 海洋甲烷球菌（Methanococcus maripaludis）的研究表明，这些蛋白是SerRS酶。因此，在本发明中， 在古细菌中发现了三种类型的SerRS。来自 嗜盐古菌Haloarcula marismortui与 细菌SerRS蛋白，而系统发育分析显示，在其他古细菌 与真核酶序列相似的不同进化枝。在 相比之下，三种产甲烷古菌含有的基因仅显示低水平的 与所有其他生物的已知Sers基因序列相似， 一种结构上不常见的酶在这个项目中，我们将详细 生物化学，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项目， 参与氨酰-tRNA合成的组分的表征 活着的王国

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.