Experimental Data Snapshot

  • Resolution: 1.95 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.222 
  • R-Value Observed: 0.222 

Starting Model: experimental
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"Dilysine Trigger" in Transferrins Probed by Mutagenesis of Lactoferrin: Crystal Structures of the R210G, R210E, and R210L Mutants of Human Lactoferrin

Peterson, N.A.Arcus, V.Anderson, B.F.Tweedie, J.W.Jameson, G.B.Baker, E.N.

(2002) Biochemistry 41: 14167

  • DOI: https://doi.org/10.1021/bi020443a
  • Primary Citation of Related Structures:  
    1H43, 1H44, 1H45

  • PubMed Abstract: 

    The mammalian iron-binding proteins lactoferrin (Lf) and transferrin (Tf) bind iron very tightly, but reversibly. Despite homologous structures and essentially identical iron binding sites, Tf begins to release iron at pH 6.0, whereas Lf retains iron to pH approximately 3.5. This difference in iron retention gives the two proteins different biological roles. Two lysine residues, Lys 206 and Lys 296, which form a hydrogen-bonded dilysine pair in human Tf, have been shown to strongly influence iron release from the N-lobe. The equivalent residues in human Lf are Arg 210 and Lys 301, and we have here mutated Arg 210 in the N-lobe half-molecule of human lactoferrin, Lf(N), to probe its role in iron release. The Lf(N) mutants R210G, R210E, and R210L were expressed, purified, and crystallized, and their crystal structures were determined and refined at resolutions of 1.95 A (R210G), 2.2 A (R210E), and 2.0 A (R210L). The overall structures are very similar to that of wild-type Lf(N), but with small differences in domain orientations. In each of the mutants, however, Lys 301 (equivalent to Lys 296 in Tf) changes its conformation to fill the space occupied by Arg 210 Neta2 in wild-type Lf(N), interacting with the two tyrosine ligands Tyr 92 and Tyr 192. By comparison with other Lf and Tf structures, we conclude that Lys 301 (or Lys 296 in Tf) only occupies this site when residue 210 (206 in Tf) is nonpositive (neutral as in R210G and R210L or negative as in R210E). Thus, Lys 206 in the Tf dilysine pair is identified as having a depressed pK(a). Three specific sites are variably occupied by polar groups in the Lf mutants and other Lf and Tf proteins, and when coupled with iron-release data, these give new insights into the factors that most influence iron retention at low pH.

  • Organizational Affiliation

    Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
LACTOFERRIN334Homo sapiensMutation(s): 1 
UniProt & NIH Common Fund Data Resources
Find proteins for P02788 (Homo sapiens)
Explore P02788 
Go to UniProtKB:  P02788
GTEx:  ENSG00000012223 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP02788
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CO3

Download Ideal Coordinates CCD File 
C O3
Query on FE

Download Ideal Coordinates CCD File 
B [auth A]FE (III) ION
Experimental Data & Validation

Experimental Data

  • Resolution: 1.95 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.222 
  • R-Value Observed: 0.222 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 131.72α = 90
b = 58.89β = 114.38
c = 57.53γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2002-11-28
    Type: Initial release
  • Version 1.1: 2011-05-08
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2023-12-13
    Changes: Data collection, Database references, Derived calculations, Refinement description