Fig 5. Analysis of newly identified HLA-I motifs.

A: Structural view of two different HLA-I alleles with N90 as in HLA-A02:20 (PDB: 2BVQ [40], pink sidechains) or K90 as in HLA-A02:01 (PDB: 2BNR [41], green sidechains). For clarity, the α₁ helix has been truncated. B: B pocket residues’ conservation across HLA-I alleles displaying preference for histidine at P2. The last line shows the sequence of HLA-B14:02, which does not show histidine preference at P2 (see motif in C), but has the same B pocket as HLA-B15:18. The last column shows amino acids at position 97, which is not part of the B pocket. C: Structural view of HLA-B14:02 in complex with a peptide with arginine at P2 (PDB: 3BVN [42]). Residues not conserved between HLA-B15:18 and HLA-B14:02 are displayed in orange. None of them are making direct contact with the arginine residue at P2. D: Stability values (half-lives) obtained for peptides with H or R at P2 for both HLA-B14:02 wt and W97R mutant. NB stands for no binding. Dashed lines indicate lower bounds for half-lives values. Residue numbering follows the one used in most X-ray structures in the PDB.