title: Presence of ferric hydroxide clusters in mutants of Haemophilus influenzae ferric ion-binding protein A.
abstract: The periplasmic iron binding protein plays an essential role in the iron uptake pathway of Gram-negative pathogenic bacteria from the Pasteurellaceae and Neisseriaceae families and is critical for survival of these pathogens within the host. In this study, we report the crystal structures of two mutant forms of ferric ion-binding protein A (FbpA) from Haemophilus influenzae with bound multinuclear oxo-metal clusters. Crystals of site-directed mutants in the metal or anion binding ligands contain protein in the open conformation, and two mutant FbpAs, H9A and N175L, contain different cluster arrangements in the iron-binding pocket. The iron clusters are anchored by binding to the two tyrosine ligands (Tyr195 and Tyr196) positioned at the vertex of the iron-binding pocket but are not coordinated by the other metal binding ligands. Our results suggest that the metal clusters may have formed in situ, suggesting that the mutant FbpAs may serve as a simple model for protein-mediated mineralization.
authors.affiliation: Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Shouldice
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Skene
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Dougan
authors.forename: Duncan E
authors.initials: DE
authors.lastname: McRee
authors.forename: Leslie W
authors.initials: LW
authors.lastname: Tari
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Schryvers
mesh_terms: D000409:Alanine / Q000235:genetics; D001216:Asparagine / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics*; D003460:Crystallization; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry*; D006193:Haemophilus influenzae / Q000737:chemistry* / Q000235:genetics; D006639:Histidine / Q000235:genetics; D033862:Iron-Binding Proteins; D007930:Leucine / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D033902:Periplasmic Binding Proteins; D011485:Protein Binding / Q000235:genetics; D012996:Solutions; D014168:Transferrin / Q000737:chemistry
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D005290:Ferric Compounds; D033862:Iron-Binding Proteins; D033902:Periplasmic Binding Proteins; D012996:Solutions; D014168:Transferrin; C021024:ferric hydroxide; D006639:Histidine; D001216:Asparagine; D007930:Leucine; D000409:Alanine