Swartzman E, Silverman M, Meighen E A
Department of Biochemistry, McGill University, Montréal, Québec, Canada.
J Bacteriol. 1992 Nov;174(22):7490-3. doi: 10.1128/jb.174.22.7490-7493.1992.
Expression of the lux operon from the marine bacterium Vibrio harveyi is dependent on cell density and requires an unlinked regulatory gene, luxR, and other cofactors for autoregulation. Escherichia coli transformed with the lux operon emits very low levels of light, and this deficiency can be partially alleviated by coexpression of luxR in trans. The V. harveyi lux promoter was analyzed in vivo by primer extension mapping to examine the function of luxR. RNA isolated from E. coli transformed with the Vibrio harveyi lux operon was shown to have a start site at 123 bp upstream of the first ATG codon of luxC. This is in sharp contrast to the start site found for lux RNA isolated from V. harveyi, at 26 bp upstream of the luxC initiation codon. However, when E. coli was cotransformed with both the lux operon and luxR, the start site of the lux mRNA shifted from -123 to -26. Furthermore, expression of the luxR gene caused a 350-fold increase in lux mRNA levels. The results suggest that LuxR of V. harveyi is a transcriptional activator stimulating initiation at the -26 lux promoter.
来自海洋细菌哈氏弧菌的lux操纵子的表达取决于细胞密度，并且需要一个不连锁的调节基因luxR和其他辅助因子进行自动调节。用lux操纵子转化的大肠杆菌发出的光水平非常低，通过反式共表达luxR可以部分缓解这种缺陷。通过引物延伸图谱在体内分析哈氏弧菌lux启动子，以检查luxR的功能。从用哈氏弧菌lux操纵子转化的大肠杆菌中分离的RNA显示在luxC的第一个ATG密码子上游123 bp处有一个起始位点。这与从哈氏弧菌分离的lux RNA的起始位点形成鲜明对比，后者在luxC起始密码子上游26 bp处。然而，当大肠杆菌用lux操纵子和luxR共转化时，lux mRNA的起始位点从-123移至-26。此外，luxR基因的表达导致lux mRNA水平增加350倍。结果表明，哈氏弧菌的LuxR是一种转录激活因子，可刺激-26 lux启动子处的起始。
