The class II associated invariant chain peptide is required for folding and localisation of MHC class II heterodimers. This domain is involved in trimerisation of the ectoderm and interferes with DM/class II binding. The trimeric protein forms a cylindrical shape which is thought to be important for interactions between the invariant chain and class II molecules [1].

1: Structure of a trimeric domain of the MHC class II-associated chaperonin and targeting protein Ii. Jasanoff A, Wagner G, Wiley DC; EMBO J. 1998;17:6812-6818. PMID:9843486