H-2Dd exploits a four residue peptide binding motif

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• The H-2Dd molecule presents endogenous peptides to T cells, crucial for immune responses.
• Understanding peptide binding motifs is essential for predicting immune recognition and designing vaccines or immunotherapies.

Purpose of the Study:

• To characterize the amino acid sequence motifs of peptides bound by the H-2Dd molecule.
• To investigate structural determinants of high-affinity peptide binding to H-2Dd.
• To explore the relationship between peptide binding and T cell epitope formation.

Main Methods:

• Characterization of endogenous peptides bound by a soluble H-2Dd analog (H-2Dds).
• Testing synthetic peptide analogs for H-2Dd binding using serologic epitope induction assays.
• Computational modeling of H-2Dds/peptide complexes based on crystallographic data.

Main Results:

• A dominant binding motif was identified: glycine at position 2, proline at position 3, and a hydrophobic residue (leucine, isoleucine, or phenylalanine) at positions 9 or 10.
• A positively charged residue at position 5 enhanced binding affinity, potentially forming a salt bridge with aspartic acid 156 on the H-2Dd heavy chain.
• Structural analysis revealed variations in the major histocompatibility complex (MHC) structure around peptide residue 1, influenced by side chain properties.

Conclusions:

• Specific amino acid sequences and structural interactions dictate high-affinity peptide binding to H-2Dd.
• Peptide positions with limited variability and low solvent accessibility are critical for binding.
• Variable peptide positions likely contribute to the formation of T cell epitopes, influencing immune responses.