翻译偶联对霍乱毒素A,B亚基比例表达的影响

目的：证实霍乱毒素操纵子Ａ，Ｂ基因间存在翻译联，解释霍乱毒素Ｂ亚基基因表达水平是Ａ亚基５倍的机理。方法；构建了适合翻译调控研究的报告质粒，通过在ｃｔｘＡ基因５’及３’端进行移码突变，研究突变对Ｂ亚基基因表达水平的影响。结果：建立合适的研究霍乱霉素基因翻译调控的系统，在ｃｔｘＡ基因的近Ｃ移码突变后，Ｂ基因的表达水平降低到１／５（８０％）。结论：霍乱霉素Ａ，Ｂ亚基基因间存在翻译联调控，这种调控是霍乱毒

Translation coupling: effect on the gene expression in the operon of cholera toxin

Objective: To demonstrate the existence of translation coupling between cholera toxin A subunit gene and B subunit gene, and to elucidate why the expression level of B gene is five times more than that of A gene. Methods: A report system for the investigation of translation coupling was constructed by using lacZ gene as the reporter, and frame shift mutation was introduced near the C terminal of ctxA gene so the ribosome would read through its normal stop codon. Results: The report plasmid was constructed and it was found that the expression level of lacZ gene decreased by five times after the frame shift mutation. Conclusion: The translation of cholera toxin B subunit gene was coupled with A subunit gene by translational coupling, and was responsible for the differential expression level of the two genes.