6AO0

CAT192 Fab Insertion Mutant H2/L2


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.208 

wwPDB Validation   3D Report Full Report


This is version 1.3 of the entry. See complete history


Literature

Structure-based engineering to restore high affinity binding of an isoform-selective anti-TGF beta 1 antibody.

Lord, D.M.Bird, J.J.Honey, D.M.Best, A.Park, A.Wei, R.R.Qiu, H.

(2018) MAbs 10: 444-452

  • DOI: https://doi.org/10.1080/19420862.2018.1426421
  • Primary Citation of Related Structures:  
    6AMJ, 6AMM, 6ANP, 6AO0

  • PubMed Abstract: 

    Metelimumab (CAT192) is a human IgG4 monoclonal antibody developed as a TGFβ1-specific antagonist. It was tested in clinical trials for the treatment of scleroderma but later terminated due to lack of efficacy. Subsequent characterization of CAT192 indicated that its TGFβ1 binding affinity was reduced by ∼50-fold upon conversion from the parental single-chain variable fragment (scFv) to IgG4. We hypothesized this result was due to decreased conformational flexibility of the IgG that could be altered via engineering. Therefore, we designed insertion mutants in the elbow region and screened for binding and potency. Our results indicated that increasing the elbow region linker length in each chain successfully restored the isoform-specific and high affinity binding of CAT192 to TGFβ1. The crystal structure of the high binding affinity mutant displays large conformational rearrangements of the variable domains compared to the wild-type antigen-binding fragment (Fab) and the low binding affinity mutants. Insertion of two glycines in both the heavy and light chain elbow regions provided sufficient flexibility for the variable domains to extend further apart than the wild-type Fab, and allow the CDR3s to make additional interactions not seen in the wild-type Fab structure. These interactions coupled with the dramatic conformational changes provide a possible explanation of how the scFv and elbow-engineered Fabs bind TGFβ1 with high affinity. This study demonstrates the benefits of re-examining both structure and function when converting scFv to IgG molecules, and highlights the potential of structure-based engineering to produce fully functional antibodies.


  • Organizational Affiliation

    a Biologics Research, Sanofi , Framingham , MA , USA.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CAT192 Fab Light chainA [auth L]216Homo sapiensMutation(s): 0 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
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  • Reference Sequence
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Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
CAT192 Fab Heavy chainB [auth H]229Homo sapiensMutation(s): 0 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
Expand
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.35 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.208 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 109.06α = 90
b = 86.59β = 100.57
c = 45.89γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
CrystalCleardata collection
SCALAdata scaling
PDB_EXTRACTdata extraction
iMOSFLMdata reduction
PHASERphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2018-01-31
    Type: Initial release
  • Version 1.1: 2018-02-14
    Changes: Database references
  • Version 1.2: 2018-05-02
    Changes: Data collection, Database references
  • Version 1.3: 2023-10-04
    Changes: Data collection, Database references, Refinement description