Plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. Can form homo- and heteropolymers with other CLDN. Homopolymers interact with CLDN3, but not CLDN1, homopolymers. Directly interacts with TJP1/ZO-1, TJP2/ZO-2 and TJP3/ZO-3 (By similarity). The disulfide bond is necessary for pore formation, but is not required for correct protein trafficking. The disease may be caused by variants affecting the gene represented in this entry. Belongs to the claudin family.