Structural Basis and Stereochemistry of Triscatecholate Siderophore Binding by FeuA

An iron will: The cyclic depsipeptide ferribacillibactin ([FeIIIBB]3−) is tightly bound by the siderophore binding protein FeuA (see picture). The FeuA/[FeIIIBB]3− complex contains a basic triad, which interacts with the triscatecholate unit of the siderophore. H2O molecules stabilize [FeIIIBB]3− in an energetically unfavored conformation. FeuA allows only a Λ configuration at the ferri-triscatecholate metal center and can thus alter the configuration of a Δ species upon binding.