Mechanism of gene activation by iron

铁（Fe）是大多数生物体的关键营养素。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合成和代谢物的合成。虽然铁是地球上最丰富的金属之一，但由于在中性pH值的有氧条件下溶解度差，几乎无法获得。在铁耗尽条件下生长期间，细菌在其环境中分泌称为铁载体的低分子量分子（称为肠杆菌素或肠螯合素），这使得铁在通过铁获取蛋白运输到细胞内之前溶解。因此，当细胞内铁水平高时，蛋白质Fur（铁摄取调节剂）抑制铁摄取基因的转录起始，铁作为辅因子。与此相反，我们已经表明，转录的几个基因被激活的条件下，高细胞内铁，或在特定的小RNA的存在下。这些基因，总共15个，分为10个操纵子。其中一些直接参与铁代谢（例如铁蛋白），而其他功能未知。铁依赖性转录激活的机制仍不清楚。我们的研究计划涉及这些基因的激活机制及其功能。

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.