Pao C C, Fleckenstein J, Dyess B T
J Bacteriol. 1981 Jan;145(1):429-33. doi: 10.1128/jb.145.1.429-433.1981.
In a wild-type strain (relA+) of Escherichia coli, starvation of amino acid led to an immediate cessation of the synthesis of stable ribonucleic acids, together with the accumulation of an unusual nucleotide, guanosine 5'-diphosphate 3'-diphosphate, commonly known as ppGpp. This compound also accumulated during heat shock. When temperature-sensitive protein synthesis elongation factor G (EF-G) was introduced into E. coli NF859, a relA+ strain, the synthesis of ppGpp was reduced to approximately one-half that of wild-type EF-G+ cells at a nonpermissive temperature of 40 degrees C. Furthermore, fusidic acid, an inhibitor of protein synthesis which specifically inactivates EF-G, prevented any accumulation of ppGpp during the heat shock. We suggest that a functional EF-G protein is necessary for ppGpp accumulation under temperature shift conditions, possibly by mediating changes in the function of another protein, the relA gene product. However, EF-G is probably not required for the synthesis of ppGpp during the stringent response, since its inactivation did not prevent ppGpp accumulation during amino acid starvation.
在大肠杆菌的野生型菌株(relA+)中,氨基酸饥饿会导致稳定核糖核酸的合成立即停止,同时会积累一种特殊的核苷酸,即5'-二磷酸鸟苷-3'-二磷酸,通常称为ppGpp。这种化合物在热休克期间也会积累。当将温度敏感型蛋白质合成延伸因子G(EF-G)导入大肠杆菌NF859(一种relA+菌株)时,在40℃的非允许温度下,ppGpp的合成降至野生型EF-G+细胞的约二分之一。此外,夫西地酸是一种蛋白质合成抑制剂,可特异性地使EF-G失活,它能阻止热休克期间ppGpp的任何积累。我们认为,功能性的EF-G蛋白对于在温度变化条件下ppGpp的积累是必需的,可能是通过介导另一种蛋白质(relA基因产物)功能的变化来实现。然而,在严紧反应期间,ppGpp的合成可能不需要EF-G,因为其失活并没有阻止氨基酸饥饿期间ppGpp的积累。