Morita Eugene Hayato, Wakamatsu Miki, Kawamoto Satsuki, Nishiyama Yoshitaka, Hayashi Hidenori
Integrated Center for Science, Ehime University, 3-5-7, Tarumi, Matsuyama 790-8566, Japan.
Nucleic Acids Res Suppl. 2003(3):203-4. doi: 10.1093/nass/3.1.203.
In cyanobacterium Synechococcus sp. PCC 7942, SmtB, functioning as the sensor to heavy-metal ions (notably Zn-ion) in the dimer form, represses the transcription of smtA gene encoding metallothionein-like protein. There are two recognition DNA sequences in the operator/promoter region of smtA gene, and the binding of SmtB with Zn-ions reduces the affinities to these sequences. This induces the activation of smtA transcription. In this study, we have studied the functional differences between these two recognition DNA sequences, with spectroscopic (hetero-nuclear NMR and UV-resonance Raman) and biochemical methods. On the basis of the results obtained here, we clarified the regulation mechanism of the smtA expression. Similar regulatory system for the tolerance to Zn-ion stress is found in another cyanobacterium. We also found that the functionally important differences between these two systems are mainly due to the structural differences of recognition DNA sequences.
在蓝藻聚球藻属PCC 7942中，SmtB以二聚体形式作为重金属离子（特别是锌离子）的传感器，抑制编码类金属硫蛋白的smtA基因的转录。smtA基因的操纵子/启动子区域有两个识别DNA序列，SmtB与锌离子的结合降低了对这些序列的亲和力。这诱导了smtA转录的激活。在本研究中，我们用光谱学方法（异核核磁共振和紫外共振拉曼）和生化方法研究了这两个识别DNA序列之间的功能差异。基于此处获得的结果，我们阐明了smtA表达的调控机制。在另一种蓝藻中发现了类似的锌离子胁迫耐受性调控系统。我们还发现这两个系统在功能上的重要差异主要是由于识别DNA序列的结构差异。
