IRON REGULATION OF SHIGA-LIKE TOXIN EXPRESSION IN ESCHERICHIA-COLI IS MEDIATED BY THE FUR LOCUS
IRON REGULATION OF SHIGA-LIKE TOXIN EXPRESSION IN ESCHERICHIA-COLI IS MEDIATED BY THE FUR LOCUS
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DOI：
10.1128/jb.169.10.4759-4764.1987
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发表时间：
1987-10-01
影响因子：
3.2
通讯作者：
MEKALANOS, JJ
中科院分区：
文献类型：
--
作者：
CALDERWOOD, SB;MEKALANOS, JJ
志贺样毒素是一种铁调节的细胞毒素，与志贺菌1的滋贺毒素非常相似。大肠杆菌中志贺样毒素的结构基因（sltA和sltB）似乎是从sltA上游的启动子转录为操纵子。我们使用启动子和sltA的近端部分与细菌碱性磷酸酶基因之间的基因融合来评估毒素表达的调节。在低铁条件下生长导致碱性磷酸酶活性增加13至16倍。然而，在毛皮基因座中存在无效突变的情况下，碱性磷酸酶活性是组成性高的，无论铁浓度如何。这些数据表明fur基因产物对slt操纵子的负调控。我们使用基因融合上游区域的缺失分析来定位slt操纵子的启动子，并显示-35和-10盒之间的DNA区域对于铁调节slt表达是必需的。在这个区域中，有一个21个碱基对的二联体重复序列，与其他三个毛皮调控基因的启动子区中的类似二联体同源。该二分体对称区域可能代表在铁存在下Fur蛋白的操纵子结合位点。
Shiga-like toxin is an iron-regulated cytotoxin quite similar to Shiga toxin from Shigella dysenteriae 1. The structural genes for Shiga-like toxin in Escherichia coli (sltA and sltB) appear to be transcribed as an operon from a promoter upstream of sltA. We used a gene fusion between the promoter and proximal portion of sltA with the gene for bacterial alkaline phosphatase to assess the regulation of toxin expression. Growth in low-iron conditions resulted in a 13- to 16-fold increase in alkaline phosphatase activity. In the presence of a null mutation in the fur locus, however, alkaline phosphatase activity was constitutively high regardless of the iron concentration. These data indicate negative regulation of the slt operon by the fur gene product. We used deletion analysis of the region upstream of the gene fusion to localize the promoter of the slt operon and to show that a region of DNA between the -35 and -10 boxes is necessary for iron regulation of slt expression. In this region, there is a 21-base-pair dyad repeat that is homologous to similar dyads in the promoter regions of three other fur-regulated genes. This region of dyad symmetry may represent an operator binding site for the Fur protein in the presence of iron.