Druger-Liotta J, Prange V J, Overdier D G, Csonka L N
J Bacteriol. 1987 Jun;169(6):2449-59. doi: 10.1128/jb.169.6.2449-2459.1987.
We isolated 60 independent mutations, designated osmX, in Salmonella typhimurium that result in constitutive expression of the normally osmoregulated proU operon. Each of the osmX mutations is closely linked to the proU locus and cis-dominant over the osmX+ allele in diploid strains. These results suggest that the mutations are probably in the 5' transcriptional control region of the proU operon. Our failure to obtain either recessive or unlinked mutations that altered the osmotic control of transcription of the proU operon suggests that transcriptional regulation of the gene is not under the negative control of a repressor protein that is dispensable for cell viability. We discuss possible models for the mechanism of osmotic regulation of transcription of the proU operon.
我们在鼠伤寒沙门氏菌中分离出60个独立的突变，命名为osmX，这些突变导致通常受渗透压调节的proU操纵子组成型表达。每个osmX突变都与proU基因座紧密连锁，并且在二倍体菌株中对osmX +等位基因呈顺式显性。这些结果表明，这些突变可能位于proU操纵子的5'转录控制区域。我们未能获得改变proU操纵子转录渗透压控制的隐性或非连锁突变，这表明该基因的转录调控不受对细胞活力可有可无的阻遏蛋白的负调控。我们讨论了proU操纵子转录渗透压调节机制的可能模型。
