Comparative study of the different mechanisms for zinc ion stress sensing in two cyanobacterial strains, Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803.
Comparative study of the different mechanisms for zinc ion stress sensing in two cyanobacterial strains, Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803.
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DOI：
10.2142/biophysics.8.103
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Hayashi H
中科院分区：
文献类型：
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作者：
Morita EH;Kawamoto S;Abe S;Nishiyama Y;Ikegami T;Hayashi H
响应于增加的Zn 2+水平，聚球藻属PCC 7942表达SmtA，一种金属硫蛋白样金属螯合蛋白，而聚球藻属PCC 6803表达ZiaA，一种Zn 2+的转运蛋白。这些蛋白的基因表达分别受阻遏蛋白SmtB和ZiaR的调控。尽管对不同的反应系统有贡献，但这两种阻遏蛋白都属于ArsR家族，并且彼此高度同源。为了了解负责处理过量Zn 2+的不同系统，我们检查了smtA和ziaA的启动子区域中的顺式元件，以及重组SmtB和ZiaR蛋白的结合亲和力。smtA的操纵子/启动子区包括两个回文序列，而ziaA包括一个回文序列。电泳迁移率变动分析表明，SmtB形成了四个不同的复合物与smtA的操作子/启动子区域，而它只形成了两个不同的复合物与ziaA的相应区域。对于ZiaR，相应的结果与SmtB的结果完全相同。此外，当Zn 2+浓度高于16 μM时，SmtB和操纵基因/启动子区域之间的复合物形成受到抑制。另一方面，相应的Zn 2+浓度为128 μM。这些结果表明，阻遏蛋白与调控基因的操纵子/启动子区之间形成蛋白-DNA复合物的程度取决于操纵子/启动子区的结构，Zn ~（2+）对这些复合物解离的影响主要与阻遏蛋白的结构有关。
In response to an increased level of Zn2+, Synechococcus sp. PCC 7942 expresses SmtA, a metallothionein-like metal-chelating protein, while Synechocystis sp. PCC 6803 expresses ZiaA, a transporter of Zn2+. The gene expression of these proteins is regulated by repressor protein, SmtB and ZiaR, respectively. In spite of contributing to different response systems, both repressor proteins belong to the ArsR family and are highly homologous to each other. To understand the different systems responsible for dealing with excess Zn2+, we examined the cis-elements in the promoter regions of smtA and ziaA, as well as the binding affinities of recombinant SmtB and ZiaR proteins. The operator/promoter region of smtA included two palindromic sequences and that of ziaA included one. Electrophoretic mobility shift assay revealed that SmtB formed four different complexes with the operator/promoter region of smtA, whereas it formed only two different complexes with the corresponding region of ziaA. For ZiaR, the corresponding results were quite the same as those for SmtB. Furthermore, the complex formation between SmtB and operator/promoter regions is inhibited in the presence of Zn2+ at higher concentrations than 16 μM. On the other hand, the corresponding Zn2+ concentration is 128 μM. These results demonstrate that the degrees of protein-DNA complex formation between repressor proteins and the operator/promoter regions of regulated genes depend on the structures of the operator/promoter regions, and the effects of Zn2+ on the dissociation of these complexes are mainly associated with the structures of the repressors.