Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

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Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 4-mer - ABCD Pseudo Symmetry: Asymmetric - C1 
Pseudo Stoichiometry: Hetero 4-mer -A2BC 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 88833.42 
• Atom Count: 6116 
• Residue Count: 801 
• Unique protein chains: 4

5HU6

Structure of the T. brucei haptoglobin-haemoglobin receptor bound to human haptolgobin-haemoglobin

• DOI: 10.2210/pdb5HU6/pdb
• Entry 5HU6 supersedes 4X0I

• Classification: TRANSPORT PROTEIN
• Organism(s): Homo sapiens, Trypanosoma brucei brucei (strain 927/4 GUTat10.1)
• Expression System: Spodoptera frugiperda, Homo sapiens, Escherichia coli


• Deposited: 2016-01-27 Released: 2016-03-02 
• Deposition Author(s): Lane-Serff, H., Higgins, M.K.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.9 Å
• R-Value Free: 0.226 
• R-Value Work: 0.190 

Re-refinement Note

This entry reflects an alternative modeling of the original data in: 

• 4X0I - determined by Lane-Serff, H., MacGregor, P., Lowe, E.D., Carrington, M., Higgins, M.K.  

Literature

Structural basis for ligand and innate immunity factor uptake by the trypanosome haptoglobin-haemoglobin receptor.

Lane-Serff, H., MacGregor, P., Lowe, E.D., Carrington, M., Higgins, M.K.

(2014) Elife 3: e05553

• PubMed: 25497229 
• DOI: 10.7554/eLife.05553
• Primary Citation of Related Structures:  
  4X0L, 4X0J, 4X0I


• PubMed Abstract: 
  

The haptoglobin-haemoglobin receptor (HpHbR) of African trypanosomes allows acquisition of haem and provides an uptake route for trypanolytic factor-1, a mediator of innate immunity against trypanosome infection. In this study, we report the structure of Trypanosoma brucei HpHbR in complex with human haptoglobin-haemoglobin (HpHb), revealing an elongated ligand-binding site that extends along its membrane distal half. This contacts haptoglobin and the β-subunit of haemoglobin, showing how the receptor selectively binds HpHb over individual components. Lateral mobility of the glycosylphosphatidylinositol-anchored HpHbR, and a ∼50° kink in the receptor, allows two receptors to simultaneously bind one HpHb dimer. Indeed, trypanosomes take up dimeric HpHb at significantly lower concentrations than monomeric HpHb, due to increased ligand avidity that comes from bivalent binding. The structure therefore reveals the molecular basis for ligand and innate immunity factor uptake by trypanosomes and identifies adaptations that allow efficient ligand uptake in the context of the complex trypanosome cell surface.

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Organizational Affiliation: 

Department of Biochemistry, University of Oxford, Oxford, United Kingdom.

Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details
Hemoglobin subunit alpha	A	141	Homo sapiens	Mutation(s): 0  Gene Names: HBA1, HBA2
Find proteins for P69905 (Homo sapiens) Go to Gene View: HBA1 HBA2 Go to UniProtKB:  P69905

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details
Hemoglobin subunit beta	B	141	Homo sapiens	Mutation(s): 0  Gene Names: HBB
Find proteins for P68871 (Homo sapiens) Go to Gene View: HBB Go to UniProtKB:  P68871

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details
Haptoglobin	C	259	Homo sapiens	Mutation(s): 0  Gene Names: HP
Find proteins for P00738 (Homo sapiens) Go to Gene View: HP Go to UniProtKB:  P00738

Entity ID: 4
Molecule	Chains	Sequence Length	Organism	Details
Haptoglobin-hemoglobin receptor	D	260	Trypanosoma brucei brucei (strain 927/4 GUTat10.1)	Mutation(s): 0
Find proteins for Q581F2 (Trypanosoma brucei brucei (strain 927/4 GUTat10.1)) Go to UniProtKB:  Q581F2

Small Molecules

Ligands 3 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram & Interactions
OXY	A, B	OXYGEN MOLECULE O2 MYMOFIZGZYHOMD-UHFFFAOYSA-N
HEM	A, B	PROTOPORPHYRIN IX CONTAINING FE HEME C34 H32 Fe N4 O4 KABFMIBPWCXCRK-RGGAHWMASA-L
NAG	C	N-ACETYL-D-GLUCOSAMINE C8 H15 N O6 OVRNDRQMDRJTHS-FMDGEEDCSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.9 Å
• R-Value Free: 0.226 
• R-Value Work: 0.190 
• Space Group: C 1 2 1

Unit Cell:

Length (Å)	Angle (°)
a = 222.290	α = 90.00
b = 56.560	β = 92.97
c = 66.100	γ = 90.00

Software Package:

Software Name	Purpose
SCALA	data scaling
BUSTER	refinement
PHASER	phasing
iMOSFLM	data reduction

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2016-01-27 
• Released Date: 2016-03-02 
• Deposition Author(s): Lane-Serff, H., Higgins, M.K.
• This entry supersedes: 4X0I

Revision History 

• Version 1.0: 2016-03-02
  Type: Initial release