STRUCTURAL STUDIES ON FPGS

这个子项目是许多研究子项目中的一个 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来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 叶酸及其衍生物是原核细胞和真核细胞生长和复制所需的必需维生素，主要通过其在一碳代谢所涉及的各种反应中的中心作用。叶酸通常以甲基和甲酰基取代基的形式作为单碳单元的载体，并且这些叶酸衍生物参与许多不同的生物化学途径，包括甲硫氨酸代谢、嘌呤核苷酸的生物合成和胸苷酸合成。 细胞内的叶酸通常以聚谷氨酸衍生物的形式存在，并且已经显示许多叶酸依赖性酶相对于单谷氨酸对聚谷氨酸化形式具有更高的亲和力。在重新合成叶酸的生物体中（例如，植物、细菌、真菌和原生动物）中，两种酶催化谷氨酸残基的加成;首先二氢叶酸合成酶（DHFS）将第一个谷氨酸残基加成到二氢蝶酸以产生二氢叶酸（DHF）。 然后，普遍存在的酶叶酸聚谷氨酸合成酶（FPGS，EC 6.3.2.17）催化所有细胞中的叶酸聚谷氨酸化，包括需要外源叶酸的那些细胞（例如，哺乳动物细胞）。 在一些细菌中，DHFS和FPGS活性存在于单个基因上（例如，大肠杆菌和棒杆菌），而在植物和真菌中，似乎有两种不同的基因编码这两种酶。从干酪乳杆菌、海栖热袍菌和双功能DHFS/FPGS E.杆菌 我们最近已经解决了结核分枝杆菌FPGS与ADP和AMPPCP复合物的结构，以及L.干酪FPGS。

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. Folic acid and its derivatives are essential vitamins required for cell growth and replication in both prokaryotic and eukaryotic cells, primarily through their central role in a variety of reactions involved in one-carbon metabolism. Folic acid serves as a carrier of single carbon units typically in the form of methyl and formyl substituents, and these folate derivatives are involved in a number of diverse biochemical pathways, including methionine metabolism, the biosynthesis of purine nucleotides and thymidylate synthesis. Folates within the cell are generally found as polyglutamate derivatives, and it has been shown that many folate-dependent enzymes have a higher affinity for the polyglutamylated forms, relative to the monoglutamate. In organisms that synthesize folates de novo (eg. plants, bacteria, fungi and protozoa), two enzymes catalyze the addition of glutamic acid residues; firstly dihydrofolate synthetase (DHFS) adds the first glutamic acid residue to dihyropteroate to produce dihydrofrolate (DHF). The ubiquitous enzyme folylpolyglutamate synthetase (FPGS, EC 6.3.2.17) then catalyzes folate polyglutamylation in all cells including those that require exogenous folate (eg. mammalian cells). In some bacteria DHFS and FPGS activity resides on a single gene (eg. Escherichia coli and Corynebacterium), whereas in plants and fungi it appears that two distinct genes encode for the two enzymes. The crystal structure of FPGS from three bacterial species have been determined from Lactobacillus casei, Thermotoga maritima and the bifunctional DHFS/FPGS E. coli. We have recently solved the structures of Mycobacterium tuberculosis FPGS in complex with ADP and AMPPCP, and three site-directed mutants of L. casei FPGS.