Structures and Mechanisms of Glutamine Dependent Enzymes

描述(由申请人提供)： 科学焦点该项目的长期目标是为谷氨酰胺转移酶的域间通讯建立一个分子基础，使其动态特性与其催化效率的控制相联系。本研究旨在描述咪唑甘油磷酸合成酶(IGPS)和鸟苷一磷酸合成酶(GMPS)这两种酶的主要机制和结构，它们催化氨从谷氨酰胺转移到嘌呤核苷酸受体底物。对于谷氨酰胺氨基转移酶亚家族的一般假设是，两个活性部位之间的功能联系涉及结合能和化学能从受体活性部位到谷氨酰胺酶部位的转导。此外，谷氨酰胺底物的特异性和催化效率由动态的蛋白质-蛋白质相互作用控制，该相互作用调节了氨转移的分子隧道。拟议的研究将集中在结构和机制信息上，以定义控制核苷酸底物激活和戊二酸水解步的时间的结构域相互作用。 目标的意义由于正在研究的代谢途径中存在的独特化学特征，以及将出现的详细的比较结构信息，该项目有可能影响新治疗药物的发现和开发。此外，这些酶代表了聚合进化的重要例子，包含了蛋白质如何远距离传递特定化学信息的许多机械细节。总体而言，提出的生化和生物物理方法的结合将：a)有助于全面了解氮代谢，b)为设计具有潜在药理意义的新的选择性药物提供关键信息，这些药物针对氨代谢中的关键酶。

DESCRIPTION (provided by applicant): Scientific Focus The long-term goals of this project are to establish a molecular basis for the interdomain communication in glutamine amidotransferases that relates their dynamic properties to the control of their catalytic efficiencies. This investigation aims to delineate the major mechanistic and structural aspects of two enzymes, imidazole glycerol phosphate synthase (IGPS), and guanosine monophosphate synthetase (GMPS), which catalyze the transfer of ammonia from glutamine to a purine nucleotide acceptor substrate. The general hypothesis under consideration for the glutamine amidotransferase sub-family is that the functional link between the two active sites involves the transduction of binding and chemical energy from the acceptor active site to the glutaminase site. Furthermore, the glutamine substrate specificity and catalytic efficiency is controlled by dynamic protein-protein interactions that modulate a molecular tunnel for ammonia transfer. The proposed studies will focus upon structural and mechanistic information to define the domain interactions that control the timing of the nucleotide substrate activation and glutarnine hydrolysis steps. Significance of objectives Because of the unique chemical features present in the metabolic pathway under investigation, and the detailed comparative structural information that will emerge, this project has the potential to impact the discovery and development of new therapeutic agents. In addition, these enzymes represent important examples of convergent evolution that hold many mechanistic details of how proteins transmit specific chemical information over large distances. Overall, the combination of biochemical and biophysical approaches proposed will: a) contribute to a comprehensive knowledge regarding nitrogen metabolism and b) provide critical information for the design of new selective agents of potential pharmacological importance that target essential enzymes in ammonia metabolism.