Mechanism of gene activation by iron

铁（Fe）是大多数生物体的关键营养物质。这种金属普遍存在于利用铁的酶的活性部位，这些酶参与代谢途径，如三羧酸（TCA）循环、呼吸、氧运输、DNA合成和代谢物合成。虽然铁是地球上最丰富的金属之一，但由于在中性ph的有氧条件下溶解度差，它几乎是不可接近的。在缺铁条件下生长的过程中，细菌在其环境中分泌低分子量分子，称为铁载体（称为肠obactin或肠螯合蛋白），这使得铁在通过铁获取蛋白运输到细胞内之前可溶解。因此，当细胞内铁水平高时，蛋白质Fur（铁摄取调节因子）抑制铁摄取基因的转录启动，铁作为辅助因子。与此相反，我们已经表明，在细胞内高铁或特定小RNA存在的条件下，几个基因的转录被激活。这些基因共有15个，分为10个操纵子。其中一些直接参与铁代谢（如铁蛋白），而其他的功能未知。这种依赖铁的转录激活机制尚不清楚。我们的研究项目涉及这些基因的激活机制以及它们的功能。

Iron (Fe) is a key nutrient for most organisms. This metal is universally present in the active site of iron-utilizing enzymes, which are involved in metabolic pathways such as the tricarboxylic acid (TCA) cycle, respiration, oxygen transport, DNA synthesis, and synthesis of metabolites. Although iron is one of the most abundant metals on earth, it is nearly inaccessible because of poor solubility in aerobic conditions at neutral pH. During growth under iron depletion conditions, bacteria secrete in their environment low-molecular weight molecules called siderophores (named enterobactin or enterochelin), which makes the iron soluble before it is transported inside the cell through iron acquisition proteins. Thus, when intracellular iron level is high, the protein Fur (Ferric uptake regulator) represses transcription initiation of iron uptake genes, with iron as a co-factor. In contrast with this, we have shown that transcription of several genes is activated under conditions of high intracellular iron, or in the presence of a specific small RNA. These genes, 15 in total, are grouped in 10 operons. Several of them are directly involved in iron metabolism (e.g. ferritin) while other have unknown function. This mechanism of iron-dependent transcriptional activation remains unclear. Our research program addresses the mechanism of activation of these genes as well as their functions.