Seyfzadeh M, Keener J, Nomura M
Department of Biological Chemistry, University of California, Irving 92717-1700.
Proc Natl Acad Sci U S A. 1993 Dec 1;90(23):11004-8. doi: 10.1073/pnas.90.23.11004.
We previously isolated a mutant of Escherichia coli that is preferentially affected in the synthesis of rRNA and has a mutation in the gene (accD) encoding a subunit of acetyl-CoA carboxylase. Using this mutant and other mutants of the pathway for fatty acid and phospholipid biosynthesis as well as cerulenin, a specific inhibitor of fatty acid synthesis, we show that (i) inhibition of fatty acid synthesis in the presence of both a carbon source and all 20 amino acids stimulates the accumulation of guanosine tetraphosphate (ppGpp) and leads to preferential inhibition of rRNA synthesis, (ii) this ppGpp accumulation is spoT dependent, and (iii) the generation of the metabolic signal that stimulates this spoT-mediated response probably does not depend on either phospholipid starvation or a significant reduction in the level of ATP.
我们之前分离出了一株大肠杆菌突变体，该突变体在rRNA合成中受到优先影响，并且在编码乙酰辅酶A羧化酶一个亚基的基因（accD）中发生了突变。利用该突变体以及脂肪酸和磷脂生物合成途径的其他突变体，还有脂肪酸合成的特异性抑制剂浅蓝菌素，我们发现：（i）在同时存在碳源和所有20种氨基酸的情况下抑制脂肪酸合成，会刺激四磷酸鸟苷（ppGpp）的积累，并导致对rRNA合成的优先抑制；（ii）这种ppGpp积累依赖于spoT；（iii）刺激这种由spoT介导的反应的代谢信号的产生可能既不依赖于磷脂饥饿，也不依赖于ATP水平的显著降低。
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