4F4O

Structure of the Haptoglobin-Haemoglobin Complex


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.9 Å
  • R-Value Free: 0.229 
  • R-Value Work: 0.211 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Structure of the haptoglobin-haemoglobin complex.

Andersen, C.B.Torvund-Jensen, M.Nielsen, M.J.de Oliveira, C.L.Hersleth, H.P.Andersen, N.H.Pedersen, J.S.Andersen, G.R.Moestrup, S.K.

(2012) Nature 489: 456-459

  • DOI: 10.1038/nature11369

  • PubMed Abstract: 
  • Red cell haemoglobin is the fundamental oxygen-transporting molecule in blood, but also a potentially tissue-damaging compound owing to its highly reactive haem groups. During intravascular haemolysis, such as in malaria and haemoglobinopathies, haem ...

    Red cell haemoglobin is the fundamental oxygen-transporting molecule in blood, but also a potentially tissue-damaging compound owing to its highly reactive haem groups. During intravascular haemolysis, such as in malaria and haemoglobinopathies, haemoglobin is released into the plasma, where it is captured by the protective acute-phase protein haptoglobin. This leads to formation of the haptoglobin-haemoglobin complex, which represents a virtually irreversible non-covalent protein-protein interaction. Here we present the crystal structure of the dimeric porcine haptoglobin-haemoglobin complex determined at 2.9 Å resolution. This structure reveals that haptoglobin molecules dimerize through an unexpected β-strand swap between two complement control protein (CCP) domains, defining a new fusion CCP domain structure. The haptoglobin serine protease domain forms extensive interactions with both the α- and β-subunits of haemoglobin, explaining the tight binding between haptoglobin and haemoglobin. The haemoglobin-interacting region in the αβ dimer is highly overlapping with the interface between the two αβ dimers that constitute the native haemoglobin tetramer. Several haemoglobin residues prone to oxidative modification after exposure to haem-induced reactive oxygen species are buried in the haptoglobin-haemoglobin interface, thus showing a direct protective role of haptoglobin. The haptoglobin loop previously shown to be essential for binding of haptoglobin-haemoglobin to the macrophage scavenger receptor CD163 (ref. 3) protrudes from the surface of the distal end of the complex, adjacent to the associated haemoglobin α-subunit. Small-angle X-ray scattering measurements of human haptoglobin-haemoglobin bound to the ligand-binding fragment of CD163 confirm receptor binding in this area, and show that the rigid dimeric complex can bind two receptors. Such receptor cross-linkage may facilitate scavenging and explain the increased functional affinity of multimeric haptoglobin-haemoglobin for CD163 (ref. 4).


    Organizational Affiliation

    Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark. cbfa@biokemi.au.dk




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Hemoglobin subunit alpha
A, D, G, J
141Sus scrofaMutation(s): 0 
Gene Names: HBA
Find proteins for P01965 (Sus scrofa)
Go to UniProtKB:  P01965
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Hemoglobin subunit beta
B, E, H, K
146Sus scrofaMutation(s): 0 
Gene Names: HBB
Find proteins for P02067 (Sus scrofa)
Go to Gene View: HBB
Go to UniProtKB:  P02067
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
Haptoglobin
C, F, I, L
347Sus scrofaMutation(s): 0 
Gene Names: HP
Find proteins for Q8SPS7 (Sus scrofa)
Go to Gene View: HP
Go to UniProtKB:  Q8SPS7
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
OXY
Query on OXY

Download SDF File 
Download CCD File 
A, B, D, E, G, H, J, K
OXYGEN MOLECULE
O2
MYMOFIZGZYHOMD-UHFFFAOYSA-N
 Ligand Interaction
FUC
Query on FUC

Download SDF File 
Download CCD File 
C, F, I, L
ALPHA-L-FUCOSE
C6 H12 O5
SHZGCJCMOBCMKK-SXUWKVJYSA-N
 Ligand Interaction
HEM
Query on HEM

Download SDF File 
Download CCD File 
A, B, D, E, G, H, J, K
PROTOPORPHYRIN IX CONTAINING FE
HEME
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
 Ligand Interaction
NAG
Query on NAG

Download SDF File 
Download CCD File 
C, F, I, L
N-ACETYL-D-GLUCOSAMINE
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.9 Å
  • R-Value Free: 0.229 
  • R-Value Work: 0.211 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 72.880α = 90.00
b = 197.780β = 90.00
c = 322.070γ = 90.00
Software Package:
Software NamePurpose
PHENIXrefinement
XDSdata scaling
XDSdata reduction
PHASERphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2012-08-29
    Type: Initial release
  • Version 1.1: 2012-09-26
    Type: Database references