Polymorphisms in pockets of major histocompatibility complex class I molecules influence peptide preference

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Major histocompatibility complex (MHC) class I molecules present peptides to cytotoxic T cells.
• Peptide binding is typically characterized by anchor residues and specific pocket interactions.
• The role of 'minor' pockets in MHC class I peptide binding specificity is not fully understood.

Purpose of the Study:

• To investigate the impact of mutations in MHC class I Kb 'minor' pockets on peptide binding.
• To determine if these mutations affect the recognition of peptides by cytotoxic T cells.
• To challenge the static model of peptide-terminus interactions within MHC class I pockets.

Main Methods:

• Utilized radiolabeled peptide libraries to probe peptide binding.
• Introduced mutations into various pockets of the MHC class I Kb molecule.
• Assessed changes in peptide preference and T cell recognition post-mutation.

Main Results:

• Mutations in all examined Kb pockets significantly affected peptide preference.
• T cell recognition of bound peptides was altered by these mutations.
• Mutations affecting main chain interactions at peptide termini also changed substrate specificity.

Conclusions:

• Minor pockets within MHC class I Kb molecules are critical for peptide selectivity.
• The interaction between peptide termini and MHC pockets is dynamic, not static.
• These findings necessitate a revised understanding of MHC class I-peptide interactions.