Jung Il Lae, Phyo Ki Heon, Kim In Gyu
Department of Radiation Biology, Environmental Radiation Research Group, Korea Atomic Energy Research Institute, 105, Yusong Taejon, 305-600, Korea.
Curr Microbiol. 2005 Jun;50(6):314-8. doi: 10.1007/s00284-005-4501-1. Epub 2005 Jun 13.
Escherichia coli tktA and tktB genes encode two transketolase isoenzymes involved in the pentose-phosphate pathway, In this study, two reporter lacZ fusions, tktA- and tktB-lacZ, were constructed to examine their transcriptional regulation on the E. coli chromosome. The tktA gene was induced in the exponential growth phase and suppressed in the stationary growth phase. However, the genetic elimination of the rpoS, whose product is an alternative sigma factor (RpoS), derepressed the tktA gene expression in the stationary growth phase, indicating that the RpoS sigma factor negatively regulates the tktA gene expression in the stationary growth phase. On the contrary, the tktB gene expression showed the highest value in the stationary growth phase and the RpoS positively regulated the tktB gene expression in the stationary growth phase. We also verified the role of the RpoS affecting the regulation of the tktA and tktB gene expression by the reverse transcription (RT)-PCR experiments. These results suggest that the differential growth-dependent expressions of the tktA and tktB genes are caused by the RpoS action.
大肠杆菌的tktA和tktB基因编码参与磷酸戊糖途径的两种转酮醇酶同工酶。在本研究中，构建了两个报告基因lacZ融合体tktA-lacZ和tktB-lacZ，以检测它们在大肠杆菌染色体上的转录调控。tktA基因在指数生长期被诱导，在稳定生长期被抑制。然而，rpoS（其产物是一种替代的σ因子（RpoS））的基因缺失在稳定生长期解除了tktA基因的表达抑制，这表明RpoS σ因子在稳定生长期对tktA基因表达起负调控作用。相反，tktB基因表达在稳定生长期达到最高值，并且RpoS在稳定生长期对tktB基因表达起正调控作用。我们还通过逆转录（RT）-PCR实验验证了RpoS对tktA和tktB基因表达调控的作用。这些结果表明，tktA和tktB基因不同的生长依赖性表达是由RpoS的作用引起的。
