Crystal structure of human transferrin bound to Triferic FPC iron pyrophosphate

Experimental Data Snapshot

  • Resolution: 2.60 Å
  • R-Value Free: 0.253 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.184 

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Ferric pyrophosphate citrate: interactions with transferrin.

Pratt, R.Handelman, G.J.Edwards, T.E.Gupta, A.

(2018) Biometals 31: 1081-1089

  • DOI: https://doi.org/10.1007/s10534-018-0142-2
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    There are several options available for intravenous application of iron supplements, but they all have a similar structure:-an iron core surrounded by a carbohydrate coating. These nanoparticles require processing by the reticuloendothelial system to release iron, which is subsequently picked up by the iron-binding protein transferrin and distributed throughout the body, with most of the iron supplied to the bone marrow. This process risks exposing cells and tissues to free iron, which is potentially toxic due to its high redox activity. A new parenteral iron formation, ferric pyrophosphate citrate (FPC), has a novel structure that differs from conventional intravenous iron formulations, consisting of an iron atom complexed to one pyrophosphate and two citrate anions. In this study, we show that FPC can directly transfer iron to apo-transferrin. Kinetic analyses reveal that FPC donates iron to apo-transferrin with fast binding kinetics. In addition, the crystal structure of transferrin bound to FPC shows that FPC can donate iron to both iron-binding sites found within the transferrin structure. Examination of the iron-binding sites demonstrates that the iron atoms in both sites are fully encapsulated, forming bonds with amino acid side chains in the protein as well as pyrophosphate and carbonate anions. Taken together, these data demonstrate that, unlike intravenous iron formulations, FPC can directly and rapidly donate iron to transferrin in a manner that does not expose cells and tissues to the damaging effects of free, redox-active iron.

  • Organizational Affiliation

    Rockwell Medical, Wixom, MI, USA. rpratt@rockwellmed.com.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Serotransferrin679Homo sapiensMutation(s): 0 
Gene Names: TFPRO1400
UniProt & NIH Common Fund Data Resources
Find proteins for P02787 (Homo sapiens)
Explore P02787 
Go to UniProtKB:  P02787
PHAROS:  P02787
GTEx:  ENSG00000091513 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP02787
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.60 Å
  • R-Value Free: 0.253 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.184 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 74.37α = 90
b = 90.16β = 90
c = 110.43γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling
PDB_EXTRACTdata extraction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2018-10-24
    Type: Initial release
  • Version 1.1: 2018-11-28
    Changes: Data collection, Database references
  • Version 1.2: 2023-10-04
    Changes: Data collection, Database references, Refinement description