1JQF

Human Transferrin N-Lobe Mutant H249Q


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.221 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Ligand variation in the transferrin family: the crystal structure of the H249Q mutant of the human transferrin N-lobe as a model for iron binding in insect transferrins.

Baker, H.M.Mason, A.B.He, Q.Y.MacGillivray, R.T.Baker, E.N.

(2001) Biochemistry 40: 11670-11675


  • PubMed Abstract: 
  • Proteins of the transferrin (Tf) family play a central role in iron homeostasis in vertebrates. In vertebrate Tfs, the four iron-binding ligands, 1 Asp, 2 Tyr, and 1 His, are invariant in both lobes of these bilobal proteins. In contrast, there are s ...

    Proteins of the transferrin (Tf) family play a central role in iron homeostasis in vertebrates. In vertebrate Tfs, the four iron-binding ligands, 1 Asp, 2 Tyr, and 1 His, are invariant in both lobes of these bilobal proteins. In contrast, there are striking variations in the Tfs that have been characterized from insect species; in three of them, sequence changes in the C-lobe binding site render it nonfunctional, and in all of them the His ligand in the N-lobe site is changed to Gln. Surprisingly, mutagenesis of the histidine ligand, His249, to glutamine in the N-lobe half-molecule of human Tf (hTf/2N) shows that iron binding is destabilized and suggests that Gln249 does not bind to iron. We have determined the crystal structure of the H249Q mutant of hTf/2N and refined it at 1.85 A resolution (R = 0.221, R(free) = 0.246). The structure reveals that Gln249 does coordinate to iron, albeit with a lengthened Fe-Oepsilon1 bond of 2.34 A. In every other respect, the protein structure is unchanged from wild-type. Examination of insect Tf sequences shows that the K206.K296 dilysine pair, which aids iron release from the N-lobes of vertebrate Tfs, is not present in the insect proteins. We conclude that substitution of Gln for His does destabilize iron binding, but in the insect Tfs this is compensated by the loss of the dilysine interaction. The combination of a His ligand with the dilysine pair in vertebrate Tfs may have been a later evolutionary development that gives more sophisticated pH-mediated control of iron release from the N-lobe of transferrins.


    Organizational Affiliation

    School of Biological Sciences and Department of Chemistry, University of Auckland, Auckland, New Zealand.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
TRANSFERRIN
A
334Homo 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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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: 1.85 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.221 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 44.200α = 90.00
b = 57.200β = 90.00
c = 135.750γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
CNSrefinement
DENZOdata reduction
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-10-17
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance