5T6P

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


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.97 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.221 
  • R-Value Observed: 0.223 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history


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
  • Structures With Same Primary Citation

  • 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 ...

    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: 2
MoleculeChainsSequence LengthOrganismDetails
Fab Fragment - Heavy ChainB, D215Mus musculusMutation(s): 0 
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  • Reference Sequence

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Fab fragment AR20.5 - Light ChainA, C216Mus musculusMutation(s): 0 
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  • Reference Sequence
  • Find similar proteins by: Sequence   |   Structure
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
MUC1 Peptide FragmentE, F8Homo sapiensMutation(s): 0 
Gene Names: MUC1PUM
Find proteins for P15941 (Homo sapiens)
Explore P15941 
Go to UniProtKB:  P15941
NIH Common Fund Data Resources
PHAROS  P15941
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.97 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.221 
  • R-Value Observed: 0.223 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 69.7α = 90
b = 69.7β = 90
c = 363.43γ = 120
Software Package:
Software NamePurpose
PHENIXrefinement
PDB_EXTRACTdata extraction
XDSdata reduction
XDSdata scaling
PHENIXphasing

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2017-01-11
    Type: Initial release
  • Version 1.1: 2017-01-18
    Changes: Derived calculations
  • Version 1.2: 2017-06-14
    Changes: Database references
  • Version 1.3: 2017-10-11
    Changes: Data collection