Biological Assembly 1  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Biological Assembly 2  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report

Global Symmetry: Cyclic - C2  (3D View)
Global Stoichiometry: Homo 2-mer - A2 

Biological assembly 2 generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 26.85 kDa 
• Atom Count: 2151 
• Modelled Residue Count: 245 
• Deposited Residue Count: 252 
• Unique protein chains: 1

4E40

The haptoglobin-hemoglobin receptor of Trypanosoma congolense

• PDB DOI: 10.2210/pdb4E40/pdb

• Classification: TRANSPORT PROTEIN
• Organism(s): Trypanosoma congolense IL3000
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2012-03-11 Released: 2013-01-16 
• Deposition Author(s): Higgins, M.K., Tkachenko, O., Brown, A., Reed, J., Carrington, M.

---

Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.60 Å
• R-Value Free: 0.223 
• R-Value Work: 0.206 
• R-Value Observed: 0.207 

Literature

Structure of the trypanosome haptoglobin-hemoglobin receptor and implications for nutrient uptake and innate immunity.

Higgins, M.K., Tkachenko, O., Brown, A., Reed, J., Raper, J., Carrington, M.

(2013) Proc Natl Acad Sci U S A 110: 1905-1910

• PubMed: 23319650 
• DOI: 10.1073/pnas.1214943110
• Primary Citation of Related Structures:  
  4E40


• PubMed Abstract: 
  

African trypanosomes are protected by a densely packed surface monolayer of variant surface glycoprotein (VSG). A haptoglobin-hemoglobin receptor (HpHbR) within this VSG coat mediates heme acquisition. HpHbR is also exploited by the human host to mediate endocytosis of trypanolytic factor (TLF)1 from serum, contributing to innate immunity. Here, the crystal structure of HpHbR from Trypanosoma congolense has been solved, revealing an elongated three α-helical bundle with a small membrane distal head. To understand the receptor in the context of the VSG layer, the dimensions of Trypanosoma brucei HpHbR and VSG have been determined by small-angle X-ray scattering, revealing the receptor to be more elongated than VSG. It is, therefore, likely that the receptor protrudes above the VSG layer and unlikely that the VSG coat can prevent immunoglobulin binding to the receptor. The HpHb-binding site has been mapped by single-residue mutagenesis and surface plasmon resonance. This site is located where it is readily accessible above the VSG layer. A single HbHpR polymorphism unique to human infective T. brucei gambiense has been shown to be sufficient to reduce binding of both HpHb and TLF1, modulating ligand affinity in a delicate balancing act that allows nutrient acquisition but avoids TLF1 uptake.

---

Organizational Affiliation: 

Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Putative uncharacterized protein	A	252	Trypanosoma congolense IL3000	Mutation(s): 0  Gene Names: TCIL3000_10_2930
UniProt
Find proteins for G0UVW6 (Trypanosoma congolense (strain IL3000)) Explore G0UVW6  Go to UniProtKB:  G0UVW6

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.60 Å
• R-Value Free: 0.223 
• R-Value Work: 0.206 
• R-Value Observed: 0.207 
• Space Group: P 6₅ 2 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 104.53	α = 90
b = 104.53	β = 90
c = 113.07	γ = 120

Software Package:

Software Name	Purpose
DNA	data collection
SHARP	phasing
REFMAC	refinement
MOSFLM	data reduction
SCALA	data scaling

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2012-03-11 
• Released Date: 2013-01-16 
Deposition Author(s): Higgins, M.K., Tkachenko, O., Brown, A., Reed, J., Carrington, M.

Revision History  

• Version 1.0: 2013-01-16
  Type: Initial release
  
• Version 1.1: 2013-02-13
  Changes: Database references