Kwangseog Ahn of Seoul National University led a group that purified protein complexes associated with MHC class I loading and found protein disulfide isomerase (PDI) in the mix of peptides.
Eisenlohr writes: "PDI plays a major role in peptide loading of MHC class I molecules by regulating the redox state of a cysteine pair in the alpha 2 domain, previously identified as an important determinant of peptide receptivity. siRNA and mutagenesis studies reveal that PDI has both peptide-binding (chaperonin) and peptide-loading functions, and that it operates as a peptide editor, ensuring the acquisition of high-affinity peptides that are stably displayed at the cell surface.
"On top of this, the...
1. B. Park et al., "Redox regulation facilitates optimal peptide selection by MHC class I during antigen processing," Cell, 127:369-82, Oct. 20, 2006.