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Mol Cell. 2009 Aug 28;35(4):523-33. doi: 10.1016/j.molcel.2009.06.029.

Insights into the bacterial transferrin receptor: the structure of transferrin-binding protein B from Actinobacillus pleuropneumoniae.

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Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.


Pathogenic bacteria from the Neisseriaceae and Pasteurellacea families acquire iron directly from the host iron-binding glycoprotein, transferrin (Tf), in a process mediated by surface receptor proteins that directly bind host Tf, extract the iron, and transport it across the outer membrane. The bacterial Tf receptor is comprised of a surface exposed lipoprotein, Tf-binding protein B (TbpB), and an integral outer-membrane protein, Tf-binding protein A (TbpA), both of which are essential for survival in the host. In this study, we report the 1.98 A resolution structure of TbpB from the porcine pathogen Actinobacillus pleuropneumoniae, providing insights into the mechanism of Tf binding and the role of TbpB. A model for the complex of TbpB bound to Tf is proposed. Mutation of a single surface-exposed Phe residue on TbpB within the predicted interface completely abolishes binding to Tf, suggesting that the TbpB N lobe comprises the sole high-affinity binding region for Tf.

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