The cytoplasmic tails of MHC class I molecules do not possess any of the known ER export sequences. BAP31 acts as a cargo receptor by exporting peptide-loaded class I MHC molecules to the ER exit sites or ER/Golgi intermediate compartment. Sec24 of the Sec23-Sec24/Sar1-GTP complex catches cargo by direct contact, forming the prebudding complex. Sar1/Sec23-Sec24 can bring about curvature of the membrane in the formation of vesicle. The cargo (antigen-bound MHC) accumulates within the COPII vesicle by binding to the Sec24 polypeptide of the COPII coat.
Spiliotis, ET, Manley, H, Osorio, M, Zúñiga, MC, Edidin, M
Stephens, DJ, Lin-Marq, N, Pagano, A, Pepperkok, R, Paccaud, JP
Hammond, AT, Glick, BS
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