Figure 2.

Iron uptake and metabolism regulated by Fur. In high iron conditions, ferrous iron (Fe²⁺) acts as a co-repressor, enhancing Fur DNA binding affinity and repressing genes involved in iron uptake to prevent toxicity. Fur can also activate genes expressing iron storage proteins by repressing the small non-coding RNA RyhB activity. Under low-iron conditions, Fur releases Fe²⁺ and dissociates from DNA, allowing the expression of siderophore synthesis genes. Without any interaction of Fur with RyhB, iron storage genes are repressed.