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

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

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinobacillus pleuropneumoniae / chemistry*
  • Actinobacillus pleuropneumoniae / genetics
  • Actinobacillus pleuropneumoniae / metabolism
  • Binding Sites
  • Crystallography, X-Ray
  • Models, Molecular
  • Mutation
  • Protein Conformation
  • Protein Structure, Tertiary
  • Transferrin / metabolism
  • Transferrin-Binding Protein B / chemistry*
  • Transferrin-Binding Protein B / genetics
  • Transferrin-Binding Protein B / isolation & purification
  • Transferrin-Binding Protein B / metabolism

Substances

  • Transferrin
  • Transferrin-Binding Protein B

Associated data

  • PDB/3HOE
  • PDB/3HOL