Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 4-mer - A1B1C1D1 Pseudo Symmetry: Asymmetric - C1 
Pseudo Stoichiometry: Hetero 4-mer - A2B1C1 

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

Macromolecule Content

• Total Structure Weight: 88.83 kDa 
• Atom Count: 6116 
• Residue Count: 784 
• 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
• Expression System: Homo sapiens, Spodoptera frugiperda, Escherichia coli
• Mutation(s): No 


• 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: 2.90 Å
• R-Value Free: 0.226 
• R-Value Work: 0.190 
• R-Value Observed: 0.192 

Re-refinement Note

This entry reflects an alternative modeling of the original data in:4X0I

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:  
  5HU6, 4X0J, 4X0L


• 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

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Hemoglobin subunit alpha	A	141	Homo sapiens	Mutation(s): 0  Gene Names: HBA1, HBA2
Find proteins for P69905 (Homo sapiens) Explore P69905  Go to UniProtKB:  P69905
NIH Common Fund Data Resources
PHAROS:  P69905 GTEx:  ENSG00000188536ENSG00000206172

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Hemoglobin subunit beta	B	141	Homo sapiens	Mutation(s): 0  Gene Names: HBB
Find proteins for P68871 (Homo sapiens) Explore P68871  Go to UniProtKB:  P68871
NIH Common Fund Data Resources
PHAROS:  P68871 GTEx:  ENSG00000244734

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details	Image
Haptoglobin	C	259	Homo sapiens	Mutation(s): 0  Gene Names: HP
Find proteins for P00738 (Homo sapiens) Explore P00738  Go to UniProtKB:  P00738
NIH Common Fund Data Resources
PHAROS:  P00738 GTEx:  ENSG00000257017

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

Small Molecules

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

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.90 Å
• R-Value Free: 0.226 
• R-Value Work: 0.190 
• R-Value Observed: 0.192 
• Space Group: C 1 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 222.29	α = 90
b = 56.56	β = 92.97
c = 66.1	γ = 90

Software Package:

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

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
  
• Version 1.1: 2020-07-29
  Type: Remediation
  Reason: Carbohydrate remediation
  Changes: Data collection, Derived calculations, Structure summary