6-pyruvoyltetrahydropterin synthase paralogs replace the folate synthesis enzyme dihydroneopterin aldolase in diverse bacteria.
6-pyruvoyltetrahydropterin synthase paralogs replace the folate synthesis enzyme dihydroneopterin aldolase in diverse bacteria.
复制标题
6-丙酮酰四氢蝶呤合酶旁系同源物取代多种细菌中的叶酸合成酶二氢蝶呤醛缩酶。
DOI：
10.1128/jb.00416-09
复制
发表时间：
2009
影响因子：
3.2
通讯作者：
Hanson,AndrewD
中科院分区：
文献类型：
--
作者：
Pribat,Anne;Jeanguenin,Linda;Lara-Núñez,Aurora;Ziemak,MichaelJ;Hyde,JohnE;deCrécy-Lagard,Valérie;Hanson,AndrewD
二氢新蝶呤醛缩酶 (FolB) 在经典叶酸生物合成途径中催化二氢新蝶呤转化为 6-羟甲基二氢蝶呤 (HMDHP)。然而，绿柔菌门、酸杆菌门、厚壁菌门、浮霉菌门和螺旋体门的某些细菌的基因组中缺少 folB 基因。几乎所有这些folB缺陷基因组都含有四氢生物蝶呤合成酶6-丙酮酰四氢蝶呤合酶(PTPS)的不寻常旁系同源物，其中谷氨酸残基取代或伴随催化半胱氨酸。来自疟原虫恶性疟原虫的类似 PTPS 旁系同源物已知在体外由二氢新蝶呤三磷酸形成 HMDHP，并已被提议为体内 FolB 步骤提供旁路。相应地，编码具有活性位点谷氨酸、半胱氨酸或这两种残基的PTPS样蛋白的细菌基因与P一起进行了测试。用于补充大肠杆菌突变的恶性疟原虫基因。 TheP。恶性疟原虫序列和带有谷氨酸或谷氨酸加半胱氨酸的细菌序列是活跃的；那些仅含有半胱氨酸的人则不然。这些结果表明，具有活性位点谷氨酸的 PTPS 旁系同源物（称为 PTPS-III 蛋白）可以在体内功能上替代 FolB。重组细菌 PTPS-III 蛋白，如 P. falciparumenzyme 介导二氢新蝶呤三磷酸向 HMDHP 的转化，但其他 PTPS 蛋白则不然。 PTPS-III 和其他 PTPS 蛋白均未表现出显着的二氢新蝶呤醛缩酶活性。系统发育分析表明，PTPS-III 蛋白可能在不同的 PTPS 谱系中独立出现。与这种可能性一致，仅仅将谷氨酸残基引入PTPS蛋白的活性位点就在生长互补测定中赋予了初始活性，并且在PTPS-III蛋白中用丙氨酸取代谷氨酸消除了互补性。
Dihydroneopterin aldolase (FolB) catalyzes conversion of dihydroneopterin to 6-hydroxymethyldihydropterin (HMDHP) in the classical folate biosynthesis pathway. However,folBgenes are missing from the genomes of certain bacteria from the phylaChloroflexi,Acidobacteria,Firmicutes,Planctomycetes, andSpirochaetes. Almost all of thesefolB-deficient genomes contain an unusual paralog of the tetrahydrobiopterin synthesis enzyme 6-pyruvoyltetrahydropterin synthase (PTPS) in which a glutamate residue replaces or accompanies the catalytic cysteine. A similar PTPS paralog from the malaria parasitePlasmodium falciparumis known to form HMDHP from dihydroneopterin triphosphate in vitro and has been proposed to provide a bypass to the FolB step in vivo. Bacterial genes encoding PTPS-like proteins with active-site glutamate, cysteine, or both residues were accordingly tested together with theP. falciparumgene for complementation of theEscherichia coli folBmutation. TheP. falciparumsequence and bacterial sequences with glutamate or glutamate plus cysteine were active; those with cysteine alone were not. These results demonstrate that PTPS paralogs with an active-site glutamate (designated PTPS-III proteins) can functionally replace FolB in vivo. Recombinant bacterial PTPS-III proteins, like theP. falciparumenzyme, mediated conversion of dihydroneopterin triphosphate to HMDHP, but other PTPS proteins did not. Neither PTPS-III nor other PTPS proteins exhibited significant dihydroneopterin aldolase activity. Phylogenetic analysis indicated that PTPS-III proteins may have arisen independently in various PTPS lineages. Consistent with this possibility, merely introducing a glutamate residue into the active site of a PTPS protein conferred incipient activity in the growth complementation assay, and replacing glutamate with alanine in a PTPS-III protein abolished complementation.