Ferric enterobactin receptor (FepA)

The **ferric enterobactin receptor** is an integral outer membrane protein in Gram-negative bacteria, best characterized as FepA in *Escherichia coli*. It belongs to the family of TonB-dependent transporters and functions as a ligand-gated channel, facilitating the high-affinity and specific uptake of ferric enterobactin (an iron-siderophore complex) from the extracellular environment into the periplasmic space. This process is essential for bacterial iron acquisition, especially under iron-limited conditions commonly encountered in host environments. The transport of ferric enterobactin through FepA is powered indirectly by the proton motive force via the TonB–ExbB–ExbD complex in the inner membrane. The specificity for FeEnterobactin is determined by the structure of the receptor’s extracellular loops and plug domain, with additional transport into the cytoplasm accomplished by an ABC transporter system. FepA and homologous receptors are widespread among Gram-negative bacteria and are studied as potential targets for novel antibiotics and as virulence determinants in infection[1][2][3][5].

Other names

FepA (gene and protein name in E. coli)Ferric enterochelin receptor (alternative older name, less common)Outer membrane iron receptor (describing the molecular function)

Ligand (siderophore, antibiotic, or toxin) binds to the extracellular loops of FepA Conformational change and interaction with the TonB energy-transducing complex Translocation of ligand (ferric-enterobactin or bacteriocin) into the periplasm