title: Insights into the bacterial transferrin receptor: the structure of transferrin-binding protein B from Actinobacillus pleuropneumoniae.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Trevor F
authors.initials: TF
authors.lastname: Moraes
authors.forename: Rong-hua
authors.initials: RH
authors.lastname: Yu
authors.forename: Natalie C J
authors.initials: NC
authors.lastname: Strynadka
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Schryvers
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014168:Transferrin / Q000378:metabolism; D033882:Transferrin-Binding Protein B / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D014168:Transferrin; D033882:Transferrin-Binding Protein B