Pocketcheck: updating the HLA class I peptide specificity roadmap

Area of Science:

• Immunology
• Structural Biology
• Computational Biology

Background:

• X-ray crystallography of peptide:HLA (human leucocyte antigen) class I complexes provides insights into peptide binding and immune response.
• Understanding these interactions is crucial for fields like transplantation and immunotherapy.

Purpose of the Study:

• To analyze structural data of peptide:HLA class I complexes to identify residues critical for peptide anchoring.
• To investigate the functional impact of specific HLA class I residue variations on peptide binding motifs.

Main Methods:

• Comparative analysis of 101 peptide:HLA class I crystal structures from the Protein Data Bank using the Contact Map Analysis webserver.
• Development of a database (Pocketcheck) for residue position, amino acid, and buried surface contact analysis.
• Utilized soluble HLA technology and mass spectrometry to analyze peptides from HLA-B*44:06.

Main Results:

• HLA class I residues 24, 45, 63, and 67 frequently contact peptide positions p1 and/or p2, suggesting a role in peptide anchor selection.
• HLA-B*44:06 exhibits distinct anchor motifs (P/A at p2, Y/W at C-terminal) and an auxiliary motif (D/E at p1) compared to HLA-B*44:02.
• Seven amino acid exchanges in HLA-B*44:06 influence its peptide binding characteristics.

Conclusions:

• Structural analysis of peptide:HLA complexes is valuable for understanding allogenicity.
• Identifying key residues and binding motifs advances strategies for intelligent HLA mismatching in clinical applications.