Miller V L, Mekalanos J J
Proc Natl Acad Sci U S A. 1984 Jun;81(11):3471-5. doi: 10.1073/pnas.81.11.3471.
We have cloned a positive regulatory gene ( toxR ) from Vibrio cholerae that controls cholera toxin transcription. This was done by first constructing a genetic fusion consisting of the lacZ gene fused to the promoter of the cholera toxin operon ctxAB . This operon fusion was used to screen a V. cholerae genomic library for genes that could activate the ctx promoter in Escherichia coli. This method allowed the identification of a gene, toxR , that increases ctx expression by more than 100-fold. Complementation analysis indicated that certain hypotoxinogenic mutants of V. cholerae 569B probably have mutations in the toxR gene. Southern blot analysis suggests that all V. cholerae, including nontoxinogenic strains, have the toxR gene. Moreover, nontoxinogenic strains not only lack the structural genes for cholera toxin but also sequences associated with the larger 7-kilobase ctx genetic element.
我们从霍乱弧菌中克隆了一个控制霍乱毒素转录的正向调节基因（toxR）。具体做法是，首先构建一个由lacZ基因与霍乱毒素操纵子ctxAB的启动子融合而成的基因融合体。这个操纵子融合体被用于筛选霍乱弧菌基因组文库，以寻找能够在大肠杆菌中激活ctx启动子的基因。通过这种方法，鉴定出了一个基因toxR，它能使ctx表达增加100倍以上。互补分析表明，霍乱弧菌569B的某些低产毒素突变体可能在toxR基因上发生了突变。Southern印迹分析表明，所有霍乱弧菌，包括无毒菌株，都有toxR基因。此外，无毒菌株不仅缺乏霍乱毒素的结构基因，还缺乏与更大的7千碱基ctx遗传元件相关的序列。
