Figure 3.

FCs in as isolated BfrB are empty (top). Soaking crystals of as isolated BfrB in Fe²⁺ solution allows observation of iron loaded FCs and of a conformational rearrangement of the H130 side chains from “gate open” (top) to “gate closed” (bottom). Soaking Fe-soaked crystals in crystallization solution causes the FCs to empty, with concomitant rearrangement of H130 from the “gate closed” to the “gate open” conformation.