(a) Comparison of the A-F pocket specificities of the HLA-A*68:02, HLA-A*02:01, H-2Kb and HLA-A*68:01 peptide binding grooves. (b) Binding of fluorescent peptide to IFNγ-treated HeLaM-HLA-ABCKO transduced with HLA-A*02:01, mouse EL4 cells (which express H-2Kb) or HeLaM-HLA-ABCKO transduced with HLA-A*68:01 -/+1 µM soluble TAPBPR variant for 15 min at 37°C, followed by incubation with 10 nM NLVPK*VATV (HLA-A2 binding peptide) for 60 min, 1 nM SIINFEK*L (H-2Kb binding peptide) for 30 min or 100 nM KTGGPIYK*R (HLA-A*68:01) for 60 min at 37°C. (c) Bar graph summarising the peptide exchange by soluble TAPBPR variants as performed in b). Error bars represent MFI -/+ SD from four independent experiments. ****p ≤ 0.0001, ***p ≤ 0.001, *p ≤ 0.05, using unpaired two-tailed t-tests. (d) Structure of MHC I from above the binding groove and the different amino acids between HLA-A*68:02 and –A*68:01 highlighted in red.