The invariant chain protein, Ii, has only one function in MHC class II antigen presentation. This function entails Ii protein occupying the peptide-binding site of each newly synthesized class II protein, thereby preventing nascent MHC class II proteins from binding peptides or misfolded proteins in the endoplasmic reticulum.

Question

Quizplus · Accepted Answer

The invariant chain (Ii) has multiple functions in MHC class II antigen presentation: besides occupying the peptide-binding site to prevent premature peptide binding, it also facilitates the proper folding of MHC class II molecules, their assembly in the endoplasmic reticulum, and their transport to the endosomal/lysosomal compartments where peptide loading occurs.

The Invariant Chain Protein, Ii, Has Only One Function in MHC