5T78

Crystal structure of therapeutic mAB AR20.5 in complex with MUC1 peptide

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 

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Literature

Glycosylation of MUC1 influences the binding of a therapeutic antibody by altering the conformational equilibrium of the antigen.

Movahedin, M., Brooks, T.M., Supekar, N.T., Gokanapudi, N., Boons, G.J., Brooks, C.L.

(2017) Glycobiology 27: 677-687

  • DOI: 10.1093/glycob/cww131
  • Primary Citation of Related Structures:  
    5T6P, 5T78

  • PubMed Abstract: 

    • In cancer cells, the glycoprotein Mucin 1 (MUC1) undergoes abnormal, truncated glycosylation. The truncated glycosylation exposes cryptic peptide epitopes that can be recognized by antibodies. Since these immunogenic regions are cancer specific, they represent ideal targets for therapeutic antibodies ...

    In cancer cells, the glycoprotein Mucin 1 (MUC1) undergoes abnormal, truncated glycosylation. The truncated glycosylation exposes cryptic peptide epitopes that can be recognized by antibodies. Since these immunogenic regions are cancer specific, they represent ideal targets for therapeutic antibodies. We investigated the role of tumor-specific glycosylation on antigen recognition by the therapeutic antibody AR20.5. We explored the affinity of AR20.5 to a synthetic cancer-specific MUC1 glycopeptide and peptide. The antibody bound to the glycopeptide with an order of magnitude stronger affinity than the naked peptide. Given these results, we postulated that AR20.5 must specifically bind the carbohydrate as well as the peptide. Using X-ray crystallography, we examined this hypothesis by determining the structure of AR20.5 in complex with both peptide and glycopeptide. Surprisingly, the structure revealed that the carbohydrate did not form any specific polar contacts with the antibody. The high affinity of AR20.5 for the glycopeptide and the lack of specific binding contacts support a hypothesis that glycosylation of MUC1 stabilizes an extended bioactive conformation of the peptide recognized by the antibody. Since high affinity binding of AR20.5 to the MUC1 glycopeptide may not driven by specific antibody-antigen contacts, but rather evidence suggests that glycosylation alters the conformational equilibrium of the antigen, which allows the antibody to select the correct conformation. This study suggests a novel mechanism of antibody-antigen interaction and also suggests that glycosylation of MUC1 is important for the generation of high affinity therapeutic antibodies.

    Organizational Affiliation: 

    Department of Chemistry, California State University Fresno, 2555 E San Ramon Ave, Fresno, CA 93740, USA.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Fab fragment AR20.5 - Light ChainA, D [auth C]216Mus musculusMutation(s): 0 
Protein Feature View
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Fab Fragment - AR20.5 - Heavy chainB, E [auth D]215Mus musculusMutation(s): 0 
Protein Feature View
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  • Reference Sequence
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
MUC1 GlycopeptideF [auth E], C [auth F]8Homo sapiensMutation(s): 0 
Gene Names: MUC1, PUM
UniProt & NIH Common Fund Data Resources
Find proteins for P15941 (Homo sapiens)
Explore P15941 
Go to UniProtKB:  P15941
PHAROS:  P15941
GTEx:  ENSG00000185499
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NGA (Subject of Investigation/LOI)
Query on NGA
Download Ideal Coordinates CCD File 
G [auth F], H [auth E]2-acetamido-2-deoxy-beta-D-galactopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-JAJWTYFOSA-N		 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 97.25α = 90
b = 100.46β = 90
c = 235.32γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
XSCALEdata scaling
PDB_EXTRACTdata extraction
XDSdata reduction
PHENIXphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2017-01-11
    Type: Initial release
  • Version 1.1: 2017-06-14
    Changes: Database references
  • Version 1.2: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Derived calculations, Structure summary