Sakai T T, Cohen S S
Proc Natl Acad Sci U S A. 1976 Oct;73(10):3502-5. doi: 10.1073/pnas.73.10.3502.
The observation that guanosine 5'-triphosphate (GTP) is an activator and guanosine 5'-diphosphate-3'-diphosphate (ppGpp) is an inhibitor of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) of Escherichia coli [E. Hölttä et al. (1974) Biochem. Biophys. Res. Commun. 59, 1104-1111] has been confirmed. The hypothesis that synthesis of both polyamine and RNA in E. coli is regulated in vivo by these nucleotides was tested in E. coli B-207. On transfer of this K+-requiring, amino-acid-deficient strigent strain from K+-medium to Na+-medium, the organism stops protein synthesis, maintains a high rate of RNA synthesis, and increases putrescine synthesis from ornithine manyfold. Under these conditions, the cells do not markedly change their contents of GTP and ppGpp. The proposed mechanism of regulation of RNA and putrescine synthesis by guanine nucleotides does not appear to explain the metabolic phenomena observed in this organism during K+ deficiency. Nevertheless, amino acid depletion in K+-medium does result in a marked increase in ppGpp.
鸟苷 5'-三磷酸（GTP）是大肠杆菌鸟氨酸脱羧酶（L-鸟氨酸羧基裂解酶，EC 4.1.1.17）的激活剂，而鸟苷 5'-二磷酸-3'-二磷酸（ppGpp）是其抑制剂，这一观察结果[E. 赫尔塔等人（197 在大肠杆菌 B-207 中对大肠杆菌体内多胺和 RNA 的合成受这些核苷酸调节的假说进行了验证。将这种需要钾离子、缺乏氨基酸的严格菌株从钾离子培养基转移到钠离子培养基后，该生物体停止蛋白质合成，维持较高的 RNA 合成速率，并使鸟氨酸合成腐胺的量增加许多倍。在这些条件下，细胞内 GTP 和 ppGpp 的含量没有明显变化。鸟嘌呤核苷酸对 RNA 和腐胺合成的调控机制似乎无法解释该生物体在钾离子缺乏期间观察到的代谢现象。然而，在钾离子培养基中氨基酸耗尽确实会导致 ppGpp 显著增加。 4）生物化学与生物物理学研究通讯 59，1104 - 1111]已得到证实。
