Iron piracy: acquisition of transferrin‐bound iron by bacterial pathogens

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Abstract
The mechanism of iron utilization from transferrin has been most extensively characterized in the pathogenic Neisseria species and Haemophilus species. Two transferrin‐binding proteins, Tbp1 and Tbp2, have been identified in these pathogens and are thought to be components of the transferrin receptor. Tbp1 appears to be an integral, TonB‐dependent outer membrane protein while Tbp2, a lipoprotein, may be peripherally associated with the outer membrane. The relative contribution of each of these proteins to transferrin binding and utilization is discussed and a model of iron uptake from transferrin is presented. Sequence comparisons of the genes encoding neisserial transferrin‐binding proteins suggest that they are probably under positive selection for variation and may have resulted from inter‐species genetic exchange.