FUNCTIONS OF tRNA MODIFICATIONS

摘要 转移RNA(TRNA)分子的修饰在转录后发生，是 促进细胞健康和生存能力。令人感兴趣的是m1G37的修改，它几乎发生在 G37碱基与反密码子序列的3‘端相邻的tRNA分子。这个 M1G37的修饰对于维持核糖体上tRNA阅读框架的特异性是重要的 蛋白质合成。这种修饰的消除会增加蛋白质合成中的核糖体错误，并提高 帧移动的频率。催化m1G37修饰的酶是tRNA(M1G37)甲基 转移酶，它将S-腺苷蛋氨酸(ADOMet)的甲基转移到G37的N1位。 TRNA。这种细菌酶被称为trmD(由trmD基因编码)，对大肠杆菌的生长是必不可少的， 鼠伤寒沙门氏菌和肺炎链球菌。最近一个意想不到的发现是，虽然TrmD是 在细菌物种中高度保守，与其真核生物几乎没有序列或结构上的同源性 和古生菌的对应物(称为trm5，由trm5基因编码)。这使TrmD和Trm5成为 一对相似的酶，它们使用不同的结构折叠来催化相同的反应，以合成 TRNA中依赖生长的m1G37。真核细菌裂解过程中TrmD和Trm5的分离 因此，古生菌提出了选择性靶向细菌TrmD的医学上相关和有吸引力的前景。 这项建议旨在提供一个强大的生化和分子基础，这是必要的 这种药物靶向的成功。该项目的两个目标是确定分子和结构基础 TrmD和Trm5对Adobe Met和tRNA的识别以及导致 催化作用。第三个目的将确定m1G37修饰在核糖体解码过程中的作用 进程。这些目标结合了目前两个不同领域的优势和利益。 (tRNA修饰的酶学，以及核糖体结构和功能)，以解决将具有 对人类健康的长期影响和对细菌病原体的生物防御。

Abstract Modifications of transfer RNA (tRNA) molecules occur after transcription and constitute an essential step to promote cellular fitness and viability. Of interest is the m1G37 modification, which takes place at almost all tRNA molecules that have the G37 base immediately adjacent to the 3' side of the anticodon sequence. The m1G37 modification is important for maintaining the tRNA reading frame specificity on the ribosome during protein synthesis. Elimination of this modification increases ribosomal errors in protein synthesis and elevates frequencies of frame shifts. The enzyme that catalyzes the m1G37 modification is tRNA(m1G37) methyl transferase, which transfers the methyl group of S-adenosyl methionine (AdoMet) to the N1 position of G37 in tRNA. The bacterial enzyme, known as TrmD (encoded by the trmD gene), is essential for growth in E. coli, Salmonella typhimurium, and Streptococcus pneumoniae. An unexpected recent finding is that while TrmD is highly conserved among bacterial species, it shares little sequence or structural homology with its eukaryotic and archaeal counterpart (known as Trm5, encoded by the trm5 gene). This establishes TrmD and Trm5 as a pair of analogous enzymes that use distinct structural folds to catalyze the same reaction to synthesize the growth-dependent m1G37 in tRNA. The separation of TrmD and Trm5 along the split of bacteria from eukarya- archaea thus raises the medically relevant and attractive prospect of selective targeting of the bacterial TrmD. This proposal is aimed at providing a strong biochemical and molecular foundation that is necessary for the success of such drug targeting. Two aims of the project are to determine the molecular and structural basis of TrmD and Trm5 for their recognition of AdoMet and tRNA and the dynamic recognition process that leads to catalysis. The third aim will determine the role of the m1G37 modification on the ribosome during the decoding process. Together, these aims combine the strengths and interests of two presently separate fields (enzymology of tRNA modification, and ribosome structure and function) to address key issues that will have long-term impact on human health and bio-defense against bacterial pathogens.