Biochemistry of lysyl-tRNA synthetases

描述（由申请人提供）：氨酰-tRNA合成酶负责氨基酸和tRNA的配对，并且对于核糖体蛋白质合成和翻译以外的其他过程都至关重要。氨酰-tRNA合成酶家族还包含许多旁系同源物，其概括了氨酰-tRNA合成酶的催化核心或各种附加结构域。在细菌中，典型的赖氨酰-tRNA合成酶提供了翻译赖氨酸密码子和修饰膜脂质的底物，而密切相关的辅基PoxA则参与延伸因子P的翻译后修饰，这是一条对沙门氏菌等病原体的毒力至关重要的途径。在这两种情况下，赖氨酰-tRNA合成酶型蛋白质促进tRNA以外的分子的赖氨酰化的能力对细胞具有广泛的影响，决定了诸如抗生素抗性等关键特性。这个建议的目的是建立在我们早期的赖氨酰-tRNA合成酶家族的工作，研究赖氨酰-tRNA合成酶及其旁系同源物的非典型作用。具体而言，我们将确定：i）赖氨酰-tRNA在lipd修饰中的作用的结构和功能基础。ii）赖氨酰-tRNA合成酶和PoxA的不同底物识别的分子基础。这项工作将揭示允许赖氨酰-tRNA合成酶家族成员参与蛋白质合成之外的氨酰化反应的分子机制，并将显示蛋白质和脂质的氨酰化如何为这些分子提供新的和必要的生物活性。了解使赖氨酰-tRNA合成酶家族在细胞中发挥如此广泛作用的结构和功能特征也将为其他氨酰-tRNA合成酶蛋白家族中可能的新功能提供见解，其中绝大多数家族包含许多保守性良好的旁系同源物，但功能未知。

DESCRIPTION (provided by applicant): The aminoacyl-tRNA synthetases are responsible for pairing amino acids and tRNAs, and are crucial both for ribosomal protein synthesis and other processes outside translation. The aminoacyl-tRNA synthetase family also contains numerous paralogs that recapitulate either the catalytic core or the various appended domains of aminoacyl-tRNA synthetases. In bacteria the canonical lysyl-tRNA synthetase provides substrates both to translate lysine codons and to modify membrane lipids, while the closely related paralog PoxA instead participates in the post-translational modification of elongation factor P, a pathway critical for the virulence of pathogens such as Salmonella. In both instances, the ability of lysyl-tRNA synthetase-type proteins to promote lysylation of molecules other than tRNA has widespread effects on the cell, determining key properties such as antibiotic resistance. The objective of this proposal is to build on our earlier work on the lysyl-tRNA synthetase family to study non-canonical roles of lysyl-tRNA synthetases and their paralogs. Specifically, we will determine: i) The structural and functional basis of lysyl-tRNA's role in lipd modification. ii) The molecular basis of divergent substrate recognition by lysyl-tRNA synthetase and PoxA. iii) The mechanism of action of modified elongation factor P. This work will reveal the molecular mechanisms that allow members of the lysyl-tRNA synthetase family to participate in aminoacylation reactions outside protein synthesis, and will show how the aminoacylation of proteins and lipids can provide these molecules with new and essential biological activities. Understanding the structural and functional features that allow the lysyl-tRNA synthetase family to play such broad roles in the cell will also provide insights into possible new functions in othe aminoacyl-tRNA synthetase protein families, the vast majority of which contain numerous well-conserved paralogs with no known function.