FIG. 3.

Proposed model of PerR-mediated iron acquisition in L. monocytogenes. PerR is constitutively expressed, and it is in a less active state (associated with Fe). When iron is limited, PerR binds to manganese (more active state; complexed with Mn) and represses fur, which consequently results in a reduction of Fur expression and upregulation of FRC genes. Broken lines indicate a change in control over FRC genes by Fur due to a decrease in expression. Alternatively, PerR in the active form may be interacting with unknown factors to cause the same effect on fur and FRC gene regulation.