García-Domínguez M, Lopez-Maury L, Florencio F J, Reyes J C
Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, E-41092 Sevilla, Spain.
J Bacteriol. 2000 Mar;182(6):1507-14. doi: 10.1128/JB.182.6.1507-1514.2000.
A gene cluster composed of nine open reading frames (ORFs) involved in Ni(2+), Co(2+), and Zn(2+) sensing and tolerance in the cyanobacterium Synechocystis sp. strain PCC 6803 has been identified. The cluster includes an Ni(2+) response operon and a Co(2+) response system, as well as a Zn(2+) response system previously described. Expression of the Ni(2+) response operon (nrs) was induced in the presence of Ni(2+) and Co(2+). Reduced Ni(2+) tolerance was observed following disruption of two ORFs of the operon (nrsA and nrsD). We also show that the nrsD gene encodes a putative Ni(2+) permease whose carboxy-terminal region is a metal binding domain. The Co(2+) response system is composed of two divergently transcribed genes, corR and corT, mutants of which showed decreased Co(2+) tolerance. Additionally, corR mutants showed an absence of Co(2+)-dependent induction of corT, indicating that CorR is a transcriptional activator of corT. To our knowledge, CorR is the first Co(2+)-sensing transcription factor described. Our data suggest that this region of the Synechocystis sp. strain PCC 6803 genome is involved in sensing and homeostasis of Ni(2+), Co(2+), and Zn(2+).
已鉴定出一个由九个开放阅读框（ORF）组成的基因簇，该基因簇参与了蓝藻集胞藻PCC 6803菌株对镍离子（Ni²⁺）、钴离子（Co²⁺）和锌离子（Zn²⁺）的感应及耐受性。该基因簇包括一个Ni²⁺响应操纵子和一个Co²⁺响应系统，以及一个先前已描述的Zn²⁺响应系统。Ni²⁺响应操纵子（nrs）的表达在Ni²⁺和Co²⁺存在时被诱导。在该操纵子的两个ORF（nrsA和nrsD）被破坏后，观察到Ni²⁺耐受性降低。我们还表明，nrsD基因编码一种推定的Ni²⁺通透酶，其羧基末端区域是一个金属结合结构域。Co²⁺响应系统由两个反向转录的基因corR和corT组成，其突变体显示出Co²⁺耐受性降低。此外，corR突变体显示不存在Co²⁺依赖性的corT诱导，这表明CorR是corT的转录激活因子。据我们所知，CorR是所描述的第一个Co²⁺感应转录因子。我们的数据表明，集胞藻PCC 6803菌株基因组的这一区域参与了Ni²⁺、Co²⁺和Zn²⁺的感应及体内平衡。
