1I6Q

Formation of a protein intermediate and its trapping by the simultaneous crystallization process: Crystal structure of an iron-saturated intermediate in the FE3+ binding pathway of camel lactoferrin at 2.7 resolution


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.255 
  • R-Value Work: 0.188 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Protein intermediate trapped by the simultaneous crystallization process. Crystal structure of an iron-saturated intermediate in the Fe3+ binding pathway of camel lactoferrin at 2.7 a resolution.

Khan, J.A.Kumar, P.Srinivasan, A.Singh, T.P.

(2001) J.Biol.Chem. 276: 36817-36823

  • DOI: 10.1074/jbc.M104343200

  • PubMed Abstract: 
  • This is the first protein intermediate obtained in the crystalline state by the simultaneous process of Fe(3+) binding and crystal nucleation and is also the first structure of an intermediate of lactoferrin in the Fe(3+) binding pathway. Lactoferrin ...

    This is the first protein intermediate obtained in the crystalline state by the simultaneous process of Fe(3+) binding and crystal nucleation and is also the first structure of an intermediate of lactoferrin in the Fe(3+) binding pathway. Lactoferrin is an iron-binding 80-kDa glycoprotein. It binds Fe(3+) very tightly in a closed interdomain cleft in both lobes. The iron-free structure of lactoferrin, on the other hand, adopts an open conformation with domains moving widely apart. These studies imply that initial Fe(3+) binding must be in the open form. The protein intermediate was crystallized by the microdialysis method. The protein solution, with a concentration of 100 mg/ml in 10 mm Tris-HCl, pH 8.0, was loaded in a capillary and dialyzed against the same buffer containing 26% (v/v) ethanol placed in a reservoir. FeCl(3) and CO(3)(2-) in excess molar ratios to that of protein in its solution were added to the reservoir buffer. The crystals appeared after some hours and grew to the optimum size within 36 h. The structure was determined by molecular replacement method and refined to final R- and R-free factors of 0.187 and 0.255, respectively. The present structure showed that the protein molecule adopts an open conformation similar to that of camel apolactoferrin. The electron density map clearly indicated the presence of two iron atoms, one in each lobe with 4-fold coordinations: two by the protein ligands of Tyr-92(433) OH and Tyr-192(526) OH and two other coordination sites occupied by oxygen atoms of bidentate CO(3)(2-) ions leading to a tetrahedral intermediate. The CO(3)(2-) anion is stabilized through hydrogen bonds with the synergistic anion-binding site Arg-121(463) and with Ser-122 Ogamma in the N-lobe and Thr-464 Ogamma in C-lobe. The third oxygen atom of CO(3)(2-) interacts with a water molecule in both lobes.


    Organizational Affiliation

    Department of Biophysics, All India Institute of Medical Sciences, New Delhi 110029, India.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
LACTOFERRIN
A
689Camelus dromedariusGene Names: LTF
EC: 3.4.21.-
Find proteins for Q9TUM0 (Camelus dromedarius)
Go to Gene View: LTF
Go to UniProtKB:  Q9TUM0
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
FE
Query on FE

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

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

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.255 
  • R-Value Work: 0.188 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 175.910α = 90.00
b = 80.620β = 92.37
c = 56.290γ = 90.00
Software Package:
Software NamePurpose
CNSrefinement
SCALEPACKdata scaling
AMoREphasing
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-11-07
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance