Section of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA.
J Bacteriol. 2011 Dec;193(23):6505-11. doi: 10.1128/JB.05681-11. Epub 2011 Sep 30.
The transcription factor Fur regulates the expression of a number of genes in Vibrio cholerae in response to changes in the level of available iron. Fur usually acts as a repressor, but here we show that Fur positively regulates the expression of ompT, which encodes a major outer membrane porin. OmpT levels increased when the bacteria were grown in medium containing relatively high levels of iron, and this effect required Fur. The level of ompT mRNA also is increased in the presence of iron and Fur. The effect of iron on OmpT levels was independent of the known ompT regulators ToxR and Crp, and it did not require RyhB, which has been shown to be responsible for positive regulation by iron of some V. cholerae genes. Electrophoretic mobility shift assays showed that Fur binds upstream of the ompT transcription start site in a region overlapping known binding sites for ToxR and Crp. These data suggest that Fur and iron positively regulate ompT expression through the direct binding of Fur to the ompT promoter.
转录因子 Fur 响应铁含量的变化，调节霍乱弧菌中许多基因的表达。Fur 通常作为一种阻遏物起作用，但在这里我们表明，Fur 正向调节编码主要外膜孔蛋白的 ompT 的表达。当细菌在含有相对高浓度铁的培养基中生长时，OmpT 的水平增加，这种效应需要 Fur。在存在铁和 Fur 的情况下，ompTmRNA 的水平也增加。铁对 OmpT 水平的影响不依赖于已知的 ompT 调节剂 ToxR 和 Crp，也不依赖于 RyhB，后者已被证明负责铁对一些霍乱弧菌基因的正向调节。电泳迁移率变动分析表明，Fur 在与已知 ToxR 和 Crp 结合位点重叠的区域结合到 ompT 转录起始位点的上游，结合到 ompT 启动子上。这些数据表明，Fur 和铁通过 Fur 与 ompT 启动子的直接结合正向调节 ompT 的表达。
