Haemophilus influenzae ferric binding protein A -Iron Loaded

Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.205 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


The role of vicinal tyrosine residues in the function of Haemophilus influenzae ferric binding protein A.

Khambati, H.K.Moraes, T.F.Singh, J.Shouldice, S.R.Yu, R.H.Schryvers, A.B.

(2010) Biochem J 

  • DOI: https://doi.org/10.1042/BJ20101043
  • Primary Citation of Related Structures:  
    3KN7, 3KN8, 3OD7, 3ODB

  • PubMed Abstract: 

    The periplasmic FbpA (ferric-binding protein A) from Haemophilus influenzae plays a critical role in acquiring iron from host transferrin, shuttling iron from the outer-membrane receptor complex to the inner-membrane transport complex responsible for transporting iron into the cytoplasm. In the present study, we report on the properties of a series of site-directed mutants of two adjacent tyrosine residues involved in iron co-ordination, and demonstrate that, in contrast with mutation of equivalent residues in the N-lobe of human transferrin, the mutant FbpAs retain significant iron-binding affinity regardless of the nature of the replacement amino acid. The Y195A and Y196A FbpAs are not only capable of binding iron, but are proficient in mediating periplasm-to-cytoplasm iron transport in a reconstituted FbpABC pathway in a specialized Escherichia coli reporter strain. This indicates that their inability to mediate iron acquisition from transferrin is due to their inability to compete for iron with receptor-bound transferrin. Wild-type iron-loaded FbpA could be crystalized in a closed or open state depending upon the crystallization conditions. The synergistic phosphate anion was not present in the iron-loaded open form, suggesting that initial anchoring of iron was mediated by the adjacent tyrosine residues and that alternate pathways for iron and anion binding and release may be considered. Collectively, these results demonstrate that the presence of a twin-tyrosine motif common to many periplasmic iron-binding proteins is critical for initially capturing the ferric ion released by the outer-membrane receptor complex.

  • Organizational Affiliation

    Department of Microbiology and Infectious Diseases, University of Calgary, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Iron-utilization periplasmic protein309Haemophilus influenzaeMutation(s): 0 
Gene Names: fbpAfbphitAHI_0097
Find proteins for P35755 (Haemophilus influenzae (strain ATCC 51907 / DSM 11121 / KW20 / Rd))
Explore P35755 
Go to UniProtKB:  P35755
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP35755
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.205 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 130.957α = 90
b = 52.515β = 90
c = 40.989γ = 90
Software Package:
Software NamePurpose
CrystalCleardata collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2010-09-15
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-11-01
    Changes: Data collection, Database references, Derived calculations, Refinement description