Part of an ABC transporter complex involved in ferric-petrobactin uptake. Probably responsible for the translocation of the substrate across the membrane. The complex is composed of two ATP-binding proteins (FatE), two transmembrane proteins (FatC and FatD) and a solute-binding protein (FpuA). A mutant lacking both fpuB and fatCD permeases is incapable of using petrobactin as an iron source and exhibits attenuated virulence in a murine model of inhalational anthrax infection. Belongs to the binding-protein-dependent transport system permease family. FecCD subfamily.