Figure 4. Intermolecular interactions among peptide-loading complex proteins.

(A) Mouse TAP1 was immunoprecipitated from cell equivalents with rabbit anti-mouse TAP1 serum (#503). The immunoprecipitated proteins were electrophoresed on a 10% acrylamide Tris-glycine gel, transferred to a membrane, and probed on a western blot with goat anti-mouse TAP1 Ab. (B) K^d molecules were immunoprecipitated from cell equivalents using the 34-1-2 mAb or the 64-3-7 mAb. The immunoprecipitated proteins were electrophoresed on a 4→20% acrylamide Tris-glycine gel (for K^d) or on a 10% acrylamide Tris-glycine gel (for tapasin, calreticulin, and ERp57). The proteins were then transferred to membranes and probed on western blots with the 64-3-7 mAb (for K^d), hamster anti-mouse tapasin mAb, rabbit anti-calreticulin polyclonal antibody, or rabbit anti-ERp57 serum. On the K^d blot, a background band occurring upon immunoprecipitation with the 34-1-2 mAb (more visible in cells with K^d) is marked with an asterisk. Noncontiguous lanes from the same gel are indicated by a dashed line. Results shown here are representative of the results from two experiments. (C) Tapasin molecules were immunoprecipitated from cell equivalents with a goat anti-mouse tapasin antibody. The immunoprecipitated proteins were electrophoresed on a 10% acrylamide Tris-glycine gel (for tapasin) or on a 4→20% acrylamide Tris-glycine gel (for K^d), transferred to membranes and probed on western blots with hamster anti-mouse tapasin mAb or with the 64-3-7 mAb (for K^d).