Important modulator in the HLA class II restricted antigen presentation pathway by interaction with the HLA-DM molecule in B-cells. Modifies peptide exchange activity of HLA-DM.
Subcellular locations: Endosome membrane, Lysosome membrane
Complexes with HLA-DM molecule during intracellular transport and in endosomal/lysosomal compartments. Heterotetramerization is necessary to exit the ER.