Fig. 5: Ligand binding modes to siderophore outer-membrane transporters.

A X-ray crystal structure of FpvA bound to pyoverdine (PDB 2W6T) (Chain A omitted for clarity). B X-ray crystal structure of PfeA (PDB 6Q5E) bound to enterobactin C X-ray crystal structure of FhuA bound to ferrichrome (PDB 1BY5) D X-ray crystal structure of FhuA bound to δ2-albomycin (PDB 1QKC). The structures show both two albomycin conformers in yellow and cyan. Yellow Zoom: binding pocket of FpvA with pyoverdine in yellow, ferric ion represented by a sphere. The orange amino acid residues correspond to hydrogen bonding interactions between the siderophore and the uptake protein, while the purple residues provide mostly alternative bonding interactions. Blue zoom: enterobactin binding pocket with interactions shown using the same colouring scheme. Pink zoom: Ferrichrome binding pocket with interactions shown. Orange zoom: albomycin binding pocket with interactions shown, the image picture omits the cyan conformer for clarity.