Part of the ABC transporter complex FhuCDB involved in iron(3+)-hydroxamate import. Responsible for the translocation of the substrate across the membrane. The complex is composed of two ATP-binding proteins (FhuC), two transmembrane proteins (FhuB) and a solute-binding protein (FhuD) (Probable). FhuB interacts with FhuC and FhuD (PubMed:1551849, PubMed:8522527, PubMed:9426146). Induced 2.1-fold by hydroxyurea. FhuD interacts with a periplasmic and a transmembrane/cytoplasmic region of FhuB. The transmembrane region may be part of a pore through which a portion of FhuD inserts into the cytoplasmic membrane during transport. Belongs to the binding-protein-dependent transport system permease family. FecCD subfamily. Truncated N-terminus.