Fig 5.

pH-titration curves of the HLA-DM-mediated dissociation of CLIP peptide from WT and H33Y HLA-DR1 and HLA-DR4 molecules. Purified HLA-DR molecules containing the WT α-chain (○) or the mutated H33Y α-chain (•) were preloaded with biotinylated CLIP peptide and incubated for 1.5 h with soluble HLA-DM (2 μM) in buffers with indicated pH. The experiment was carried out with soluble HLA-DR1 (Left) as well as with soluble HLA-DR4 (Right) in the presence of HA306–318 peptide. After the release the amount of stable HLA-DR/biotinylated CLIP was determined by ELISA as described in Fig. 3B.