FUNCTIONS OF tRNA MODIFICATIONS

摘要 转运RNA（tRNA）分子的修饰发生在转录后，构成转录的重要步骤。 促进细胞健康和活力。有趣的是m1 G37修改，几乎所有版本都进行了修改 具有紧邻反密码子序列3'侧的G37碱基的tRNA分子。的 m1 G37修饰对于在转录过程中维持核糖体上的tRNA阅读框特异性是重要的。 蛋白质合成消除这种修饰会增加蛋白质合成中的核糖体错误， 帧移位的频率。催化m1 G37修饰的酶是tRNA（m1 G37）甲基 转移酶，其将S-腺苷甲硫氨酸（Met）的甲基转移到G37的N1位置， tRNA。这种细菌酶被称为TrmD（由trmD基因编码），是大肠杆菌生长所必需的。大肠杆菌， 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 它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同源性。 和古细菌对应物（称为Trm 5，由trm 5基因编码）。这将TrmD和Trm 5确定为 一对类似的酶，使用不同的结构折叠来催化相同的反应，以合成 tRNA中的生长依赖性m1 G37。TrmD和Trm 5的分离沿着细菌从真核细胞中的分裂- 因此，古生菌提出了选择性靶向细菌TrmD的医学相关和有吸引力的前景。 这项建议旨在提供一个强大的生物化学和分子基础，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Trm 5识别TCMet和tRNA，以及动态识别过程， 催化作用第三个目标是确定m1 G37修饰在核糖体上的作用 过程总之，这些目标联合收割机结合了两个目前分离的领域的优势和利益 （tRNA修饰的酶学，核糖体结构和功能），以解决关键问题， 对人类健康和细菌病原体的生物防御的长期影响。

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.