3IU3

Crystal structure of the Fab fragment of therapeutic antibody Basiliximab in complex with IL-2Ra (CD25) ectodomain

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.90 Å
  • R-Value Free: 0.262 
  • R-Value Work: 0.215 
  • R-Value Observed: 0.217 

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Literature

Structural basis for the blockage of IL-2 signaling by therapeutic antibody basiliximab

Du, J., Yang, H., Zhang, D., Wang, J., Guo, H., Peng, B., Guo, Y., Ding, J.

(2010) J Immunol 184: 1361-1368

  • DOI: 10.4049/jimmunol.0903178
  • Primary Citation of Related Structures:  
    3IU3

  • PubMed Abstract: 

    • IL-2 signaling plays a central role in the initiation and activation of immune responses. Correspondingly, blockage of this pathway leads to inhibition of the immune system and would provide some therapeutic benefits. Basiliximab (Simulect), a therapeuti ...

    IL-2 signaling plays a central role in the initiation and activation of immune responses. Correspondingly, blockage of this pathway leads to inhibition of the immune system and would provide some therapeutic benefits. Basiliximab (Simulect), a therapeutic mAb drug with specificity against IL-2R alpha of T cells, was approved by U.S. Food and Drug Administration in 1998. It has been proven to be effective in the suppression of the IL-2 pathway and hence has been widely used to prevent allograft rejection in organ transplantation, especially in kidney transplants. In this study, we report the crystal structure of the basiliximab Fab in complex with the ectodomain of IL-2R alpha at 2.9 A resolution. In the complex structure, the Fab interacts with IL-2R alpha with extensive hydrophobic and hydrophilic interactions, accounting for a high binding affinity of 0.14 nM. The Ag binding site of basiliximab consists of all six CDR loops that form a large binding interface with a central shallow hydrophobic groove surrounded by four hydrophilic patches. The discontinuous epitope is composed of several segments from the D1 domain and a minor segment from the D2 domain that overlap with most of the regions responsible for the interactions with IL-2. Thus, basiliximab binding can completely block the interactions of IL-2 with IL-2R alpha and hence inhibit the activation of the IL-2 signal pathway. The structural results also provide important implications for the development of improved and new IL-2R alpha-targeted mAb drugs.

    Organizational Affiliation: 

    State Key Laboratory of Molecular Biology, Research Center for Structural Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Heavy chain of Fab fragment of Basiliximab A, C, H215Mus musculus, Homo sapiens
This entity is chimeric		Mutation(s): 0 
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Light chain of Fab fragment of Basiliximab B, D, L210Mus musculus, Homo sapiens
This entity is chimeric		Mutation(s): 0 
Find proteins for P01834 (Homo sapiens)
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Go to UniProtKB:  P01834
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PHAROS:  P01834
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
Interleukin-2 receptor alpha chain I, J, K223Homo sapiensMutation(s): 0 
Gene Names: IL-2Ra, IL2RA
Find proteins for P01589 (Homo sapiens)
Explore P01589 
Go to UniProtKB:  P01589
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PHAROS:  P01589
GTEx:  ENSG00000134460
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  • Reference Sequence
Oligosaccharides

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Entity ID: 4
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
E, F, G
3 N-Glycosylation Oligosaccharides Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.90 Å
  • R-Value Free: 0.262 
  • R-Value Work: 0.215 
  • R-Value Observed: 0.217 
  • Space Group: P 65 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 137.051α = 90
b = 137.051β = 90
c = 459.095γ = 120
Software Package:
Software NamePurpose
HKL-2000data collection
PHASERphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2010-01-26
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2014-02-05
    Changes: Source and taxonomy
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Database references, Derived calculations, Structure summary