Svitil A L, Cashel M, Zyskind J W
Department of Biology, San Diego State University, California 92182.
J Biol Chem. 1993 Feb 5;268(4):2307-11.
Guanosine 3',5'-bispyrophosphate (ppGpp) accumulates in bacteria in response to either amino acid or energy source starvation. Here we demonstrate that levels of ppGpp similar to those induced by amino acid starvation inhibit the rate of protein synthesis by 84-91%. The intracellular concentration of ppGpp is manipulated in our studies by increasing the expression of a truncated relA gene encoding a smaller but catalytically active peptide with ppGpp synthetase activity. We find that the intracellular activity of the truncated RelA peptide is insensitive to chloramphenicol, unlike the product of the wild-type relA gene, ppGpp synthetase I. Previously, this same ppGpp expression system was used (Schreiber, G., Metzger, S., Aizenman, E., Roza, S., Cashel, M., and Glaser, G. (1991) J. Biol. Chem. 226, 3760-3767) to demonstrate that increasing the ppGpp concentration inhibits growth and ribosomal RNA transcription, and they found suggestive evidence for ppGpp inhibition of protein synthesis. We further investigated the effect of ppGpp on protein synthesis and find that ppGpp is a potent inhibitor of protein synthesis as well as glycerol accumulation but has no effect on transport of methionine, the amino acid used in measuring protein synthesis rates, or on uptake of alpha-methylglucoside, a non-metabolizable analogue of glucose.
鸟苷3',5'-双焦磷酸（ppGpp）在细菌中因氨基酸或能源饥饿而积累。在此我们证明，与氨基酸饥饿诱导水平相似的ppGpp水平可使蛋白质合成速率降低84 - 91%。在我们的研究中，通过增加编码具有ppGpp合成酶活性的较小但具有催化活性肽的截短relA基因的表达来调控ppGpp的细胞内浓度。我们发现，与野生型relA基因产物ppGpp合成酶I不同，截短的RelA肽的细胞内活性对氯霉素不敏感。此前，同一ppGpp表达系统曾被用于（施赖伯，G.，梅茨格，S.，艾曾曼，E.，罗扎，S.，卡舍尔，M.，和格拉泽，G.（1991年）《生物化学杂志》226，3760 - 3767）证明增加ppGpp浓度会抑制生长和核糖体RNA转录，并且他们发现了ppGpp抑制蛋白质合成的暗示性证据。我们进一步研究了ppGpp对蛋白质合成的影响，发现ppGpp是蛋白质合成以及甘油积累的有效抑制剂，但对用于测量蛋白质合成速率的氨基酸甲硫氨酸的转运或对葡萄糖的非代谢类似物α-甲基葡萄糖苷的摄取没有影响。
