As previously mentioned, siderophores serve the essential function of iron acquisition for pathogens in the low iron conditions of the host. Thus the successful establishment of disease depends on the ability of the invading organism to acquire iron. Because of its high affinity for iron, yersiniabactin can solubilize the metal bound to host binding proteins and transport it back to the bacteria. The complex yersiniabactin-Fe3+ recognizes the specific bacterial outer membrane TonB-dependent receptor, FyuA (Psn), and is translocated with the help of membrane-embedded proteins into the cytosol where the iron is discharged from yersiniabactin and used in various metabolic pathways. In the absence of a high-affinity iron-chelating compound, pathogenic Yersinia, responsible for such lethal disease as the bubonic plague, only causes local symptoms of moderate intensity. The availability of iron, through an intrinsic high-affinity iron-chelating system such as Ybt, provides the bacteria with the ability to multiply in the host and to cause systemic infections.
