Structural comparison of major histocompatibility complex class I molecules and homology modelling of five distinct human leukocyte antigen-A alleles

The peptide complexes of 19 major histocompatibility complex class I alpha 1 and alpha 2 domains have been compared to identify similarities that can be interpreted as constraints necessary for the function or stability of the molecule. It was found that nearly half of the residues maintained their side-chain conformations (or had no side chain), with the remaining residues being highly solvent exposed and/or polymorphic. Seven hydrogen bonds between the molecule and peptide are conserved in all the structures and serve to orientate the ends of the peptide in the binding groove. Furthermore, the general orientations of most residue side chains in the peptide are similar. Based on these constraints, homology models for the distinct human leukocyte antigen-A alleles A*0302, A*2403, A*2603, A*3101 and A*8001 have been constructed and the implications for peptide binding discussed. The models provide a useful framework from,which to engineer allele-specific peptides with a high binding affinity.