Unexpected Interaction of a Siderophore with Aluminum and Its Receptor

Hypothetical model of ferripyoverdine uptake by FpvA (TonB and ExbBD are not shown for clarity) based on the discovery of rapid recycling of pyoverdine (PVD), suggesting that it is not transported to the cytoplasm (5, 14, 15). Ferripyoverdine is bound to FpvA and is transported via the proton motive force relayed by TonB; once it is in the periplasm, a still-undescribed reduction process takes place and Fe²⁺ is bound to a periplasmic binding protein which delivers it to an ABC transporter. Ga-pyoverdine and Al-pyoverdine also can be transported but are not further processed in the periplasm.