Chemistry and functional role of the invariant chain.

The invariant chain has two critical properties that regulate the function of the class II glycoproteins with which it associates. It prevents class II molecules from binding antigenic peptides during the early stages of their assembly and transport, and it contains a signal that drives the assembled class II-invariant chain complex to an endocytic compartment. Dissociation of the invariant chain in this compartment is believed to generate class II molecules capable of binding antigenic peptides.