PURE UNDER CARBON DIOXIDE

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 生化研究和基因组分析大肠杆菌和原鸡羧基氨基咪唑核糖核苷酸脱氢酶（PurE）表明，这些嘌呤生物合成酶提供了一个不寻常的例子，在一个高度保守的，主要的代谢途径的进化分歧。I类PurE，以E为代表。在大多数原核生物和真菌中发现的大肠杆菌蛋白质，催化CO（2）基团从N5-羧基氨基咪唑核糖核苷酸（N5-CAIR）的氨基甲酸酯可逆转移到C4，产生4-羧基氨基咪唑核糖核苷酸（CAIR）。另一方面，以G.在高等真核生物中发现的一种酶，通过CO（2）可逆地转化为氨基咪唑核糖核苷酸（AIR）形成CAIR。 目前的结构研究涉及I类PurE（N5-羧基氨基咪唑变位酶），重点是其化学上独特的变位酶反应。 一个工作机制假说涉及组氨酸（大肠杆菌中的His 45）。coliPurE）作为一般酸起作用，但没有获得多个质子化状态的证据。 结构的研究对于更好地理解其作用机理具有重要意义。 我们正在特别研究His 45突变体的结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Biochemical studies and genomic analyses of the Escherichia coli and Gallus gallus carboxyaminoimidazole ribonucleotide synthases (PurEs) indicate that these purine biosynthetic enzymes provide an unusual example of evolutionary divergence in a highly conserved, primary metabolic pathway. Class I PurEs, typified by the E. coli protein and found in most prokaryotes and fungi, catalyze the reversible transfer of a CO(2) group from the carbamate of N5-carboxyamino imidazole ribonucleotide (N5-CAIR) to C4, yielding 4-carboxy aminoimidazole ribonucleotide (CAIR). On the other hand, class II PurEs, typified by the G. gallus enzyme and found in higher eukaryotes, form CAIR by reversible transfer of CO(2) to aminoimidazole ribonucleotide (AIR). The current structural study involves class I PurE (N5-carboxyaminoimidazole mutase) with an emphasis on its chemically unique mutase reaction. A working mechanistic hypothesis involves a histidine (His45 in E. coli PurE) functioning as a general acid, but no evidence for multiple protonation states has been obtained. The structural study will be very important for getting a better understanding of the mechanism. We are in particular studying the structures of the mutants of His45.