2GTW

Human Class I MHC HLA-A2 in complex with the nonameric Melan-A/MART-1(27-35) peptide having A27L substitution

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.55 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.181 
  • R-Value Observed: 0.183 

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This is version 1.2 of the entry. See complete history. 


Literature

Structures of MART-1(26/27-35) Peptide/HLA-A2 Complexes Reveal a Remarkable Disconnect between Antigen Structural Homology and T Cell Recognition

Borbulevych, O.Y., Insaidoo, F.K., Baxter, T.K., Powell, D.J., Johnson, L.A., Restifo, N.P., Baker, B.M.

(2007) J Mol Biol 372: 1123-1136

  • DOI: 10.1016/j.jmb.2007.07.025
  • Primary Citation of Related Structures:  
    2GT9, 2GTZ, 2GTW, 2GUO

  • PubMed Abstract: 

    • Small structural changes in peptides presented by major histocompatibility complex (MHC) molecules often result in large changes in immunogenicity, supporting the notion that T cell receptors are exquisitely sensitive to antigen structure. Yet there are ...

    Small structural changes in peptides presented by major histocompatibility complex (MHC) molecules often result in large changes in immunogenicity, supporting the notion that T cell receptors are exquisitely sensitive to antigen structure. Yet there are striking examples of TCR recognition of structurally dissimilar ligands. The resulting unpredictability of how T cells will respond to different or modified antigens impacts both our understanding of the physical bases for TCR specificity as well as efforts to engineer peptides for immunomodulation. In cancer immunotherapy, epitopes and variants derived from the MART-1/Melan-A protein are widely used as clinical vaccines. Two overlapping epitopes spanning amino acid residues 26 through 35 are of particular interest: numerous clinical studies have been performed using variants of the MART-1 26-35 decamer, although only the 27-35 nonamer has been found on the surface of targeted melanoma cells. Here, we show that the 26-35 and 27-35 peptides adopt strikingly different conformations when bound to HLA-A2. Nevertheless, clonally distinct MART-1(26/27-35)-reactive T cells show broad cross-reactivity towards these ligands. Simultaneously, however, many of the cross-reactive T cells remain unable to recognize anchor-modified variants with very subtle structural differences. These dichotomous observations challenge our thinking about how structural information on unligated peptide/MHC complexes should be best used when addressing questions of TCR specificity. Our findings also indicate that caution is warranted in the design of immunotherapeutics based on the MART-1 26/27-35 epitopes, as neither cross-reactivity nor selectivity is predictable based on the analysis of the structures alone.

    Organizational Affiliation: 

    Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA.



Macromolecules
Find similar proteins by: 
(by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
HLA-A*0201 heavy chain A, D275Homo sapiensMutation(s): 0 
Gene Names: HLA-A, HLAA
Find proteins for P04439 (Homo sapiens)
Explore P04439 
Go to UniProtKB:  P04439
NIH Common Fund Data Resources
PHAROS:  P04439
GTEx:  ENSG00000206503
Protein Feature View
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  • Reference Sequence
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(by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Beta-2-microglobulin B, E100Homo sapiensMutation(s): 0 
Gene Names: B2M, CDABP0092, HDCMA22P
Find proteins for P61769 (Homo sapiens)
Explore P61769 
Go to UniProtKB:  P61769
NIH Common Fund Data Resources
PHAROS:  P61769
GTEx:  ENSG00000166710
Protein Feature View
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  • Reference Sequence
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Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
octapeptide from Melan-A/MART-1 C, F9N/AMutation(s): 1 
Find proteins for Q16655 (Homo sapiens)
Explore Q16655 
Go to UniProtKB:  Q16655
NIH Common Fund Data Resources
PHAROS:  Q16655
GTEx:  ENSG00000120215
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.55 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.181 
  • R-Value Observed: 0.183 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 58.309α = 90
b = 84.271β = 90.11
c = 84.293γ = 90
Software Package:
Software NamePurpose
Blu-Icedata collection
HKL-2000data reduction
MOLREPphasing
REFMACrefinement
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2007-06-12
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance