Independent and synergistic effects of disulfide bond formation, beta 2-microglobulin, and peptides on class I MHC folding and assembly in an in vitro translation system.

We have examined the post-translational processing, intrachain disulfide bond formation, folding, and assembly of MHC class I H chains with beta 2-microglobulin after coupled in vitro translation of homogeneous mRNA and transport of nascent chains into canine microsomal vesicles. The formation of native alpha 3 domain conformation was dependent on conditions that optimized intrachain disulfide bond formation, and efficient folding of the alpha 1 alpha 2 domain required exposure to antigenic peptide. beta 2-microglobulin and peptide acted synergistically in forming native alpha 1 alpha 2 domain structure, and a small proportion of molecules with native alpha 1 alpha 2, but non-native alpha 3 structure were detected, indicating that alpha 3 domain folding is not an absolute prerequisite for the formation of native alpha 1 alpha 2 domain structure.