INVESTIGATIONS OF REACTIONS OF PHYSIOLOGICAL IMPORTANCE

这个项目涉及翻译中遗传信息的解码。具体地说，该项目的重点是通过氨基酰tRNA合成酶催化的氨基化反应来确定遗传密码的作用。在这些反应中，氨基酸与其同源转移RNA相匹配，后者包含密码子的反密码子三联体。转移RNA是被认为是在RNA世界中发展起来的古老分子，而合成酶很可能是随着遗传密码的建立而从RNA世界中出现的早期蛋白质之一。很多工作都是为了理解翻译编辑中依赖于RNA的氨基酸区分。在这个反应中，通过依赖RNA对相似氨基酸的区分进行细化，提高了密码的准确性。这里，合成酶-tRNA复合体作为核糖核蛋白(RNP)在氨基酸识别中发挥作用，这可能使人想起合成酶作为RNPs的早期发展。第二个目标是了解合成酶中的结构域如何在合成酶-tRNA复合体中进行通信。大致来说，tRNA的两个主要结构域分别与tRNA合成酶中的两个结构域相互作用。特别是，原始合成酶被认为是由一个催化结构域代表的，该催化域识别氨基酸连接位点附近的核苷酸决定因素。这种相互作用足以催化被称为微螺旋的RNA寡核苷酸底物的氨基酰化，微螺旋仅基于tRNA的可接受末端。受体茎中的核苷酸决定因素和结合的氨基酸之间的关系构成了氨基酸的可操作的RNA颂歌，它不同于遗传密码的核苷酸三联体。对于某些合成酶，其第二结构域与tRNA的第二反含结构域的相互作用以未知的机制极大地提高了氨基酰化的速度。第三个目标是看看氨基酰化微螺旋底物是否可以在无核糖体的系统中用于多肽合成。这样的系统可能代表了蛋白质合成的早期系统。总而言之，这些研究扩大了我们对遗传密码和作为其基础的生化机制的理解。它们还为RNA世界和蛋白质剧场之间可能的联系提供了线索。由于它们是必需的，并在进化过程中显示出物种特有的变异，合成酶和tRNAs是针对感染病原体的治疗药物的理想靶点。因此，扩大对这些系统的了解可以直接应用于人类健康。

This project deals with the decoding of genetic information in translation. Specifically, the project focuses on the establishment of the roles of the genetic code by the aminocylation reactions that are catalyzed by aminoacyl tRNA synthetases. In these reactions, amino acids are matched with their cognate transfer RNAs which contain the anti- codon triplets of the code. The transfer RNAs are ancient molecules that are thought to have developed in an RNA world, while the synthetases were likely among the early proteins to emerge from an RNA world as the genetic code was established. Much effort is directed at understanding RNA-dependent amino acid discrimination in translational editing. In this reaction, the accuracy of the code is enhanced through an RNA- dependent refinement of the discrimination of closely similar amino acids. Here, the synthetase-tRNA complex functions in amino acid recognition as a ribonucleoprotein (RNP) that is perhaps reminiscent of an early development of synthetases as RNPs. A second goal is to understand how domains within a synthetase communicate, within the synthetase-tRNA complex. To a rough approximation, the two major domains of a tRNA interact separately with two domains in a tRNA synthetase. In particular, the primordial synthetase is thought to be represented by a catalytic domain that recognizes nucleotides determinants near the amino acid attachment site. This interaction is sufficient to catalyze aminoacylation of RNA oligonucleotide substrates known as microhelices that are based on just the accepted end of the tRNA. The relationship between nucleotide determinants in acceptor stems and the attached amino acid constitutes an operational RNA ode for amino acids that is distinct from the nucleotide triplets of the genetic code. For some synthetases the interaction of its second domain with the second anti-contain domain of the tRNA greatly enhances the rate of the aminoacylation by an unknown mechanism. A third goal is to see whether aminoacylated microhelix substrates can be used for peptide synthesis, in a ribosome- free system. Such a system could be representative of an early system for protein synthesis. Collectively, these investigations expand our understanding of the genetic code and the biochemical mechanisms that are its underpinnings. They also give clues into the possible connections between the RNA world an the theater of proteins. Because they are essential and show species-specific variations through evolution, the synthetases and tRNAs are ideal targets for therapeutic drugs directed at infectious pathogens. An expanded understanding of these systems could, therefore, have direct applications to human health.