Fig. 2.

Metalloregulatory mechanisms expressed during high and low intracellular iron concentrations in Campylobacter. High levels of intracellular iron induce activity of the holo (iron-bound) form of transcriptional regulators Fur and PerR. Low levels of intracellular iron result in the apo form of these regulators and the derepression of genes previously repressed. Low iron also induces increased expression of transporters for the uptake of iron molecules, including ferric–enterobactin (CtuA), transferrin (CeuBCDE/CfrA), and heme (ChuZABCD). Positive regulators of these systems, such as HeuR, also become active under iron-limited conditions.