Role of transmembrane domain interactions in the assembly of class II MHC molecules.

Evidence is presented that suggests a role for transmembrane domain interactions in the assembly of class II major histocompatibility complex (MHC) molecules. Mutations in the transmembrane domains of the class II MHC alpha or beta chains resulted in proteins that did not generate complexes recognized by conformation-dependent antibodies and that were largely retained in the endoplasmic reticulum. Insertion of the alpha and beta transmembrane domains into other proteins allowed the chimeric proteins to assemble, suggesting a direct interaction of the alpha and beta transmembrane domains. The interactions were mediated by a structural motif involving several glycine residues on the same face of a putative alpha helix.