Bacterial Lactoferrin Receptors in the Neisseriaceae

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SummaryIn order to survive in the iron-restricted environment of the host, bacteria have evolved efficient mechanisms for acquisition of iron from the host’s glycoproteins, transferrin (Tf) and lactoferrin (Lf). Tf receptors, which are involved in acquisition of iron specifically from host Tf, have been identified in a number of important human and veterinary pathogens from the families Neisseriaceae and Pasteurellaceae. In contrast, receptors for the host’s Lf have only been demonstrated in Neisseriaceae. Polymerase chain reaction (PCR)-based approaches for identification of the Lf receptor genes can help overcome the limitations of growth studies, and binding and affinity isolation assays for confirming the presence of the Lf receptor-mediated pathway Affinity isolation studies have demonstrated that, contrary to previous conclusions, the composition of the Lf receptor is similar to that of the Tf receptor (Tbp1 and Tbp2) and includes two proteins, Lbp1 (Tbp1 homolog) and Lbp2 (Tbp2 homolog). The parallels in composition of receptors and organization of the genetic loci for the Tf and Lf receptors enable us to propose a model for the structure and organization of the iron-acquisition pathway. Although prior studies have provided some insights into ligand-receptor interaction, further analysis will need to incorporate modifications in order to include assessment of binding by Lbp2 and will most effectively be addressed by analysis of recombinant chimeric proteins.