Two different, highly exposed, bulged structures for an unusually long peptide bound to rat MHC class I RT1-Aa

• Published in: Immunity (Cambridge, Mass.) Vol. 14; no. 1; pp. 81 - 92
• Main Authors: Speir, J A, Stevens, J, Joly, E, Butcher, G W, Wilson, I A
• Format: Journal Article
• Language: English
• Published: United States 01.01.2001
• Subjects: Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - immunology; Animals; Crystallography, X-Ray; Epitopes, T-Lymphocyte - chemistry; Epitopes, T-Lymphocyte - immunology; Histocompatibility Antigens - chemistry; Histocompatibility Antigens - immunology; Histocompatibility Antigens Class I - chemistry; Histocompatibility Antigens Class I - immunology; Minor Histocompatibility Antigens - chemistry; Minor Histocompatibility Antigens - immunology; Mitochondrial Proton-Translocating ATPases; Models, Molecular; Peptides - chemistry; Peptides - immunology; Protein Structure, Secondary; Rats
• ISSN: 1074-7613
• DOI: 10.1016/S1074-7613(01)00091-7

The rat MHC class Ia molecule RT1-Aa has the unusual capacity to bind long peptides ending in arginine, such as MTF-E, a thirteen-residue, maternally transmitted minor histocompatibility antigen. The antigenic structure of MTF-E was unpredictable due to its extraordinary length and two arginines that could serve as potential anchor residues. The crystal structure of RT1-Aa-MTF-E at 2.55 A shows that both peptide termini are anchored, as in other class I molecules, but the central residues in two independent pMHC complexes adopt completely different bulged conformations based on local environment. The MTF-E epitope is fully exposed within the putative T cell receptor (TCR) footprint. The flexibility demonstrated by the MTF-E structures illustrates how different TCRs may be raised against chemically identical, but structurally dissimilar, pMHC complexes.