1OQH

Crystal Structure of the R124A mutant of the N-lobe human transferrin


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.219 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Structural and functional consequences of binding site mutations in transferrin: crystal structures of the Asp63Glu and Arg124Ala mutants of the N-lobe of human transferrin

Baker, H.M.He, Q.-Y.Briggs, S.K.Mason, A.B.Baker, E.N.

(2003) Biochemistry 42: 7084-7089

  • DOI: 10.1021/bi020689f
  • Primary Citation of Related Structures:  1OQG

  • PubMed Abstract: 
  • Human transferrin is a serum protein whose function is to bind Fe(3+) with very high affinity and transport it to cells, for delivery by receptor-mediated endocytosis. Structurally, the transferrin molecule is folded into two globular lobes, represen ...

    Human transferrin is a serum protein whose function is to bind Fe(3+) with very high affinity and transport it to cells, for delivery by receptor-mediated endocytosis. Structurally, the transferrin molecule is folded into two globular lobes, representing its N-terminal and C-terminal halves, with each lobe possessing a high-affinity iron binding site, in a cleft between two domains. Central to function is a highly conserved set of iron ligands, including an aspartate residue (Asp63 in the N-lobe) that also hydrogen bonds between the two domains and an arginine residue (Arg124 in the N-lobe) that binds an iron-bound carbonate ion. To further probe the roles of these residues, we have determined the crystal structures of the D63E and R124A mutants of the N-terminal half-molecule of human transferrin. The structure of the D63E mutant, determined at 1.9 A resolution (R = 0.245, R(free) = 0.261), showed that the carboxyl group still binds to iron despite the larger size of the Glu side chain, with some slight rearrangement of the first turn of alpha-helix residues 63-72, to which it is attached. The structure of the R124A mutant, determined at 2.4 A resolution (R = 0.219, R(free) = 0.288), shows that the loss of the arginine side chain results in a 0.3 A displacement of the carbonate ion, and an accompanying movement of the iron atom. In both mutants, the iron coordination is changed slightly, the principal change being in each case a lengthening of the Fe-N(His249) bond. Both mutants also release iron more readily than the wild type, kinetically and in terms of acid lability of iron binding. We attribute this to more facile protonation of the synergistically bound carbonate ion, in the case of R124A, and to strain resulting from the accommodation of the larger Glu side chain, in the case of D63E. In both cases, the weakened Fe-N(His) bond may also contribute, consistent with protonation of the His ligand being an early intermediate step in iron release, following the protonation of the carbonate ion.


    Organizational Affiliation

    School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Serotransferrin
A
337Homo sapiensGene Names: TF
Find proteins for P02787 (Homo sapiens)
Go to Gene View: TF
Go to UniProtKB:  P02787
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
K
Query on K

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Download CCD File 
A
POTASSIUM ION
K
NPYPAHLBTDXSSS-UHFFFAOYSA-N
 Ligand Interaction
FE
Query on FE

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Download CCD File 
A
FE (III) ION
Fe
VTLYFUHAOXGGBS-UHFFFAOYSA-N
 Ligand Interaction
CO3
Query on CO3

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Download CCD File 
A
CARBONATE ION
C O3
BVKZGUZCCUSVTD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.219 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 43.930α = 90.00
b = 57.120β = 90.00
c = 135.250γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
DENZOdata reduction
AMoREphasing
CNSrefinement

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-03-18
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2018-01-24
    Type: Structure summary