Bacteria use small molecules called siderophores to scavenge iron. Siderophore-Fe3+
complexes are recognised by outer-membrane transporters and imported into the periplasm
in a process dependent on the inner-membrane protein TonB. The siderophore enterobactin
is secreted by members of the family Enterobacteriaceae, but many other bacteria including
Pseudomonas species can use it. Here, we show that the Pseudomonas transporter PfeA
recognises enterobactin using extracellular loops distant from the pore. The relevance of this …