Plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. Directly interacts with TJP1/ZO-1, TJP2/ZO-2 and TJP3/ZO-3 (PubMed:10601346). Interacts with CLDN1, CD81 and OCLN (By similarity). Expressed mostly in embryonic tissues. Belongs to the claudin family.